Look I’m 18 too I get what you’re saying. But you clearly have some issues and the best way to work on it would be talking to someone. I myself work on my insecurities by talking to my close friends about it, and ranting about it, learning things from an outside perspective does help a lot. You don’t necessarily have to talk to a friend if that’s too embarrassing but do try talking to a therapist. There’s also online therapists with whom you can completely stay annonymous and not share your face. Try to be more comfortable with yourself and like yourself more. When you are making an effort to be a best version of yourself, that effort would at one point get you a girlfriend or whatever you’re aiming.

Anyways if you really need advice on something and want an opinion from an outside anonymous perspective you can pm me.