confused and sad

hey just an intro, Iam a girl and Iam 18. its been a while since ive talked to someone about all these feelings ive been getting lately. Iv been sad for such a long time now, its been years since I felt truly happy, and it really saddens me cuz I actually want to get better but I just cant, I hate this feeling of not knowing where I stand in life, I see all my friends go to college, get married, move on with their lives and I am over here crippled, not knowing what to do. The pain started off as emotional but now its getting physical, I find it hard to get out of bed and do normal things any normal person  can do. I feel like a burden to everyone around me, including my parents, i feel so sad and depressed all the time and i hate it, i wish i was normal. I have a bunch of friends but  I dont feel like I belong you know.. Ive been cutting off alot of people recently and Im losing one person after the other. I am also taking a year off before university right now so im completely isolated, i always go to the library and read or write other than that, I completely isolate myself, my friends used to ask and get worried but now theyre kinda used to it I guess and I havent heard from some of them for months.  I also broke up with my bf a year ago and Im still not over it, and his a big part of this since he put me through hell and left me feeling used and worthless and his just doing fine now, he made me really happy and when he left I felt a thousand times shittier than I did before him. home is another story since I have a pretty shitty relationship with my parents and siblings and I just cant fix it, its too broken to fix. I kinda just wanna run away to a different place and start a new life but Im scared this depression will follow through, its like something I cant get rid off, and the worst part of it all is I know for a fact that things wont get better, i try to convince myself but i know it wont, itll only get worse and worse and I know I will end up killing myself and as much as I hate to admit it I know its true. Im so desperate for anything good to happen, but its been so long and nothings changing. Iam scared of having an average life or dying alone and I have a feeling thats how I will end up if I dont kill myself, I picture myself as a 50 year old person in a home alone, with no family or friends and once I die I will soon be forgotten. Ive tried committing a few times before but it all failed and I dont know what to do anymore. Iam supposed to start uni soon but I have a feeling I wont live till then. Iam so sorry this is too long but I just needed to vent since no one I know irl knows about this, they all just think Iam lazy or something. I hope this made sense iM really high rn and Idk what Im doing but thanks alot for listening anyway.

Love,

A