How do you learn to accept your flaws and not let them eat you alive?

I am going through some serious body image and self esteem issues right now. I just feel so hideous and incompetent every day and constantly compare myself to others (and feel like everyone is better than me in every way, not even just physically). I am really hyperfixating on flaws that cannot be changed, or at least not easily and inexpensively. Every time I see someone who is better than me in these regards, I feel so insecure and inferior, and it deeply bothers me. I have an overwhelming need to be perfect and the best, and feel as though my worth is diminished if anyone is better than me in any way, or has any better features/traits at all. Obviously, this is making me miserable, because I'm nowhere near a supermodel or a genius, so of course there are a lot of people out there who are better than me.

I won't go to therapy because TBH, that's a big part of what has me like this in the first place. I had a horrible experience and went in with normal puberty problems and came out with wrecked self esteem and confidence, and also drugged on SSRIs. I'm not willing to do that again.

I don't think I know anyone as self-loathing as I am. :( My internal dialogue insults me regularly, calling myself ugly, stupid, unlikeable, etc.

I'm way too old for this teenage insecurity shit and it's ruining my life. I don't even know if it's possible to fix at this point.