At Wits end with youngest who has suspected ADHD. Need help with toileting and sleeping.

My youngest (4) daughter M, we think has suspected ADHD. She is the youngest of 3, with the 2 older siblings being age 4 and 6. We aren't getting much support from nursery as they say they can't see it and that she is just loud and hyper, they have continually told us to not bother getting help from GP as it wouldn't be suitable, and that we are too focused on trying to 'label' her as something 'wrong' (we aren't but we can see there is a huge difference between her behaviour and our other children who are also very 'hyper/boisterous'). For context she is very cute and people dote/fuss over her, so nursery staff struggle to 'see anything wrong with her' as in their words 'she is just too cute/special'. In public she gets a lot of sweets/money/attention as people find her very cute, they tend to ignore my other two children. They also don't diagnose children under 6 with ADHD where we are so we are lost with where to get support from.

I will rant my reason's below why I suspect she has ADHD, but I'll start with what we really need some advice on at the moment, sorry for the long post but I'm really lost about how to handle all of this, I am trying my best to parent her and I understand that if she does indeed have ADHD I cannot parent her the same way I do my older 2 children.

Toileting - She has been day time potty trained since she was 2.5 and had no issues at the start. She is still in nappies at night as she wets the bed multiple times a night otherwise. For around 10 months now, she has multiple accidents a day, both wet and soiled. She doesn't mind being soiled and won't tell you that she has had an accident until you notice. It seems like she is too engrossed in play, too distracted or can't be bothered to go to the toilet. Being wet/soiled doesn't bother her enough to deter her from doing it. She does it at nursery also and goes through around 5 pairs of underwear in 1 day, with a lot of days her coming back from nursery with a sore bum as nursery staff haven't noticed quick enough to clean her up. Nursery staff go between saying this is normal, all children struggle with toileting, to maybe she is constipated, or maybe she has an upset stomach or maybe she was too busy to go. To solve this at nursery we have asked staff to remind her every 30 mins - which helps some days. Is there anything else we could be doing? Most days she absolutely stinks of piss, our other children notice and make comments but she is so unbothered by it all. We don't even want to start night time potty training her, as she hasn't had a dry day in over 6 months.

Sleeping - she has always struggled sleeping through the night, and breastfeed through the night until she was 3. (Which she really didn't want to stop, but we had enough, she still struggles with the transition and almost a 1.5 years later still asks for boobies/boobie cuddle/milk, which we say no to and she has a tantrum about almost every morning). She shares a room with our other 4 year old, who sleeps through the night. Failing asleep is easy, we just do our bedtime routine, put her in bed, kiss both girls goodnight and walk out, its staying asleep that is hard. She moves around the bed a lot and we had her on a floor bed for a long time as she always fell out of the bed through the night. We now have her on a raised single bed with rails so that she doesn't fall. But now she gets trapped under the blanket because when she moves around the blanket doesn't due to the rails on the bed, so we have now put her in a sleep sack. She is up multiple times a night for every reason under the sun, I'm scared, Its dark, I need to tell you something (then proceeds to tell you a joke), I want a story, I want a cuddle, I want to play with sister, I need to sit, I want water (her bottle is in the bed with her every night), my pillow isn't right... Last night she was up between midnight and 3 am. If you don't give in to her request for example listen to my joke, the screaming starts, she is shouting no no no, kicking and fighting, I hold my boundary that I'm not getting up in the middle of the night to listen to a joke and tell her to go back to bed, and we have this battle for hours until she finally gives up. Then during the day she is upset with me because I didn't listen to her joke last night. How can I help her to sleep better, but also to just not be a nuisance to everyone else, trying to wake everyone up. If I don't micromanage her, she will just wake up her sister/everyone else in the house. She is the first up in the morning, and will have a tantrum if she has no one to play with. If we are trying to rest she is at the bottom of our bed having a tantrum because she wants someone to play with and its a battle most mornings.

Why we suspect ADHD:
She is always on the move, not sitting still for longer than a few minuets, loves to run, jump, climb, shout, sing, talk, all day long. We have a trampoline, indoor swing, sensory mats, spinning chair, and she goes between them while also scooting, riding her bike, listening to music very loudly, climbing the couch, swinging off the curtains/door handles, not giving others a chance to speak, because she just speaks/shouts over everyone.

She has a poor attention span. At meal times she is up out of her chair throughout the meal, dancing, running around the table, going under the table to tickle peoples toes, we have recently got her a highchair as meal times were unbearable as a family because we spent the whole time asking her to sit, to eat, to stop. We have found the high chair has helped as she can't physically get out, so we are spending less of meal times 'telling her off'. Getting ready is a chore, if you do not have your hands on her at all times while getting her ready, she will run off to do other things. While our other 2 children have no problems following instructions like take of your pj's, put them in the basket and put these clothes on. If you give her the same instructions, she will take of her pj's run around the house naked trying to 'fart' on people, put her pants on her head, put toothpaste on her face etc. She cannot join in with family games, as she gets bored within 2 mins and wants to run around instead. When she is playing with her siblings, if they are building with lego/magnetiles, she will build for a few mins, then when the boredom kicks in, she will threaten to knock down siblings builds, and proceed to mock them if they get upset with her. When she has to do something that requires waiting or takes time she 'needs to go to the toilet' which we let her go, but she just walks aimlessly around the house, she does this at meal times, when asked to tidy up or do any chores, or during her swimming lessons when she must wait her turn (the lessons are only 30 mins long, but every time she is asked to wait her turn, I get radioed to take her to the toilet because she has asked the instructor to go to the toilet, which I take her and she doesn't do anything, she just sits on the pan and sings). Asking her to tidying up is a battle, she will do literally anything else instead of tidy, older siblings get frustrated with this as they think its unfair that she doesn't do her fair share of tidying.

She is very emotional, will have many tantrums a day, about what feels like very trivial things. Screaming no! kicking and punching the ground. We have tried to teach regulation skills, and always offer help with cuddles, deep breathing etc. This works for our other 2 children, but she is just so angry every day. If she is told no, she will scream and fight and try to beg you to say yes. She is very talkative and imaginative, will often make up stories and make up jokes. But is weary of strangers and cries when left alone. She struggles to do anything independently, if siblings want some space or we are busy with something she will have a tantrum and scream no in our faces because she doesn't want to be left alone.

We are really struggling with the thought of her potentially having a disability. We are unsure if we are prepared to support her. We are a very active family, out most days and if in the house, playing the the garden/riding bikes/running/ exercising/playing, so she gets plenty of stimulation and play. We are screen free and spend most of our days playing/exploring. We love her very much, she is hilarious, creative, and bold, but parenting her is a chore and we are tired. We feel like we have a baby in the house, but she is almost 5 and will be going to school next year. Doing things as a family is starting to feel unenjoyable, as we are just constantly micromanaging her. Siblings are getting fed up too, as they think she gets a lot more special attention and she is constantly mocking them or winding them up or ruining their stuff or not sharing or not tidying up. Thank you if you have read the whole thing, I guess this is as much as rant as it is a cry for help.