I'm in need of opinions, I think?

I'm not asking for diagnosis or anything just want to see if anyone here is similar?

I'm unaware if I have bipolar or if I'm just mentally buggered; I took a few online screening test and did some lets say slightly obsessive research on mental disorders (mostly bipolar).

As a kid I wasn't diagnosed persay but the school nurse told my teachers and mum I was ADHD or she highly thinks I was (I did 70% of those symptoms and still do some) I don't believe anyone in my family was diagnosed with bipolar disorder and I don't want to ask because my mum will freak out and keep asking questions about why I want to know which'll make me uncomfortable and stuff, but moving on I read it can occur during stressful times, head injuries and just happen without piror genetics etc.

I've had a few head injuries before, one requiring hospital to put a gash in the back of my head together, and my whole life has been stressful to me. My parents spilt when I was like 3 or 4, my mother worries and always go to the worst outcome etc, my father doesn't seem to care I exsist or about my thoughts (maybe that's just me he doesn't show much emotion), My siblings buillied and tormented me (still abuse me today i.e. occasional threats of violence, insults etc) one of them has thrown a sharp pole like a javilyn at me and hit my leg, He's also grab a saw and threatened to cut my leg off, occasional talk of "I could totally kill someone" He is absolutely crazy imo. I know he'll be in prison one day I just know it. Not to mention the time I almost drowned or I think I did, (Trouble remembering day to day things) So all that stress factoring in.

I started noticing these bipolar symptoms in my last two years of secondary school, which was 4 years ago now I think?

Before you say it, I know online isn't a sure diagnosis and stuff, But from what I looked up, I seem to inhibit symptoms of mania, I rarely get depression but it happens. I'll try my best to try to explain my rattled brain.

I get mostly normal days (To me I don't really feel a lot of anything really) On random occasions I'll get rapid mood swings I'll be super tired at 9pm and lay down to sleep but instantly like a shot of caffeine I'm wide awake with thousands of ideas racing through my mind, I can't focus on them for very long, I'll start writing up ideas for stories and games, I feel like I can write this story and stick to it. But in a few hours I'll get a heart sinking feeling, I'll start shaking only if I'm angry at something. Then I'll lay in bed for a few hours feeling worthless then suddenly I'm really happy, no racing thoughts just happy. Sometimes I am very irritable, inpatient and quick to anger <- most common one.

It's completely random too, I've had a friend in college ask if I was bipolar cause my whole tone, mood, body language switched in a second, He said I was really chilled out and giggling etc then snapped into the tensed up anger mixed with a sad look then I walked off without saying goodbye. I shrugged and mumbled "I dunno" I then did that same thing another six nights in a row, I've also had people run up to me asking me to calm down and why i was so angry but then I was like "I'm fine? I'm not angry?" and I'd get a weird look.

I struggle to keep friends because of the switches I say things I don't mean or have no empathy for anything in that state.

Sorry for the long post, I'd like your thoughts (I'm also terrified to go to therapy or a professional to get a diagnosis) I haven't left my house for at least 4 months too...

(edit: I forgot my age, gender etc if that's important. I'm 20, Male, 6ft 4in, and a "fatty boom batty" That sounded funny in my head I am a fat guy tho)