A couple years ago I used to beat my girlfriend
No way you could do that. Did she do things to make you want to hit her?
I'm upset with her sometimes, I never hit her in the head or face!
It doesn't matter where you strike your gf, beating your partner is never okay. Apologize to her and get some help with anger management from a professional.
My girlfriend deserved it.
I think it's wise to get into therapy or turn yourself in before you might do something more harmful to her. It is never okay to hit your partner no matter what they did to you.