Please. I don’t know how to deal with this ive got no experience on it

My girlfriend has broken up with me. We were together for just shy of a year which isn’t as long as many people on here but this was my first ever actual relationship. I was head over heels for her and could see myself marrying her and settling down with kids and we talked about it all and laid out our plans for it all. We had a couple rocky moments as all types of relationships do but we moved over them easily and as recently as 3 days ago we were out lying on a picnic blanket giggling and holding each other and now it’s gone. I genuinely don’t know how to cope with this. I look to the future and can’t even see one for myself without her and even if I could see it I don’t want it. I know that the best thing is to talk to people but I can’t. I’m an 18 year old English man, friends don’t really talk about this sorta stuff in depth. I don’t have the sort of relationship with my parents that I’m easily comfortable to talk to them about everything. She was the first person I felt able to open up to and that took a lot of building up for me to be able to even word my emotions. We have one mutual friend who’s really close to both of us that I do feel able to talk to but he’s in the middle of moving house to a nearby city for him and his gfs uni. I really don’t know how to move through this and any advice would really really help please