Why am I so angry/violent when my girlfriend talks to other boys?

Honestly, I think you need anger management or counselling. While not uncommon, this is not 'normal' behaviour. You need to trust her, AND trust that she will be able to handle herself if anything happens. To worry is one thing, but to be so controlling and out of control i another. You have already seen how scared of you she is. If she were to post her POV on here, you know everyone would be telling her to leave you. What happens if one day your temper snaps and you hurt not only the guy, but her as well? Prove to her that you love her enough to get help, or... Walk away before you hurt her. I'm talking not just physically this time, but emotionally and mentally as well. I dated a man like you for two years, and he destroyed me. I can say from experience that the fear and misery truly ruins a person. Since you are on here seeking help, obviously you love her more than my ex ever loved me. You can change, and need to before it's too late. If you would like to talk more, you can always email.