If I become single again I think I’ll kill myself

I’m already really depressed I’ve had depression and anxiety my whole life but it is seasonal affective disorder it’s only been severe the last 4-5 years but every year I get it it gets worse. Last year I mostly cut and was depressed but my symptoms cleared up for the summer and then I started dating my boyfriend and then my depression I thought cleared up. But then my boyfriend cheated on me not physical but over text and it broke me. He’s apologized and was sincere that’s a whole other story but I’ve not quite gotten over it. I haven’t told anyone that I know because I have a very small circle just immediate family one friend and my boyfriend. I hyped him up so much to them that I can’t just tell them this happened a few months ago. My depression this year has been the worst by far. It completely takes over me sometimes I feel like I’ll throw up I feel so worthless and unloved even by him and at the same time if we were ever to break up I think that would be it for me. He’s the only one I talk to I have no real friends other than the one but we barely talk anymore and she has other friends she doesn’t need me. Like my boyfriend I’ll tell him how depressed I am and he will talk to me over text and that’s about it but when we first started dating and he told his ex and she said she got depressed he left work to go make sure she was okay. But I’m not worth that. I don’t know why I ever thought I would be that’s not how my life works I get the bare minimum from people even though I bend over backwards for them.im not mad about that I’m just saying if I were to die my boyfriend could just go back to her. Also without him I have no reason no purpose I mean now I’m working toward an apartment with him and a life a marriage and children but without him no one will want me I’m too far and ugly. I might as well die then because I’m just ganna be alone and die alone anyways. Idk where I got to with this I honestly feel like ending it now. I have my own dorm room and no one will bother me or try to stop me no one even cares lol. I texted no one today and no shocker dry phone all day. I’m so stressed out with school and my relationship and my self and I feel like I’m drowning I just want peace. I’m sorry for my rant I’m sure even you have better things to do than to listen to such a worthless piece of shit. I’m sorry.