I just can't anymore (long sorry!)

This probably sounds stupid asf but I've never had a bf (I'm 21), never had sex, never really experienced love of any kind aside from family love. My friends in the past and my current best mate have always put me second. I was never a priority and I'm still not a priority. My best friend atm has reconnected with some old friends who weren't there when she was in her abusive relationship (but I was) and lately she doesn't even really wanna talk to me about anything other than her current relationship. She doesn't ask me about stuff that's going on in my life, only calls me to vent, it feels so one sided and cause she's my only friend I feel I don't have anyone to talk to. As said before I've never had a bf, I've come close a couple of times but in the end they realise I'm not enough for them. The concept of having someone who cares for me relationship wise is so foreign, when people say oh I love cuddling my bf/gf I don't get it cause I've never experienced it. I'm worried I never will. What if I never find it cause I'm not good enough? I can't imagine anyone ever finding me attractive or fun or likes me for me. It's been a shit few months, this entire summer was spent getting over a guy who rejected me cause of my appearance and that I'm too dull for him, I'm just starting to feel better but I'm worried if I delete the dating app & stop talking to guys that I'll never get anywhere. I honestly don't know how much more I can take, this feeling of not being enough for anyone. I'm glad I have my mum, she's the only person in my life who makes me feel that I'm good enough but one day she's not gonna be around, when I move out etc I'm gonna have to face being alone a lot more but it's scaring me. Why do the guys I connected with always lose interest? Why does my best friend feel I'm not enough to even be her friend but instead someone who's just there when nobody else is? I just can't anymore😔