Gf was drunk yesterday and admitted I had the smallest peepee she's been with

She sounds kinda c*nty to be honest with you

I get drunk lots of times and I would never tell a girl "you need to lose weight" or "you're bad in bed" or something hurtful like that.

This sounds like cope, but I genuinely believe that, for 99% of women, peepee size just does not matter.

It kinda sounds like she was trying to hurt you. That sucks, but it's not your fault, and you shouldn't be depressed about it. Why be depressed when another person hurts you? That's their problem, not yours.

God knows I am depressed but it's because of my own shortcomings, not because other people try to hurt me. Their slings & arrows just run off me like water off a duck's back. Am I torturing this metaphor enough?

I hesitate to tell you, "break up with her" because that's such a stereotypical Reddit thing to say but if she's such an abusive alcoholic that she would intentionally try to injure you in such a way? Eh, maybe it's warranted. I mean, would you get drunk and tell a girl, "you're fat and ugly" just to hurt her feelings? I don't know you, but I don't think you would. Do you want to put up with an abusive person? That's up to you.

tl;dr: it's not your problem, it's her problem. Adopt an attitude of arrogance and pride. If the outside world calls you inadequate, don't feel sorry for yourself, tell the outside world, "frick you."