Dear Insensitive Fool,
Well, the first step in getting help is recognizing that you have a problem. And most males don't realize they have or admit they have a problem.
You Can't Get Help Alone
Since you realize that you have a problem with your anger, you should seek professional help. You can try and do it on your own but that never works. Not only will this help benefit your girlfriend, but you also.
She Will Leave You
As for your girlfriend, you are lucky she is still with you. I have personally been in this type of relationship and sooner or later, she will leave. And that is even more devastating because of your jealousy issues.
No Excuse for Mistreating Someone
So from this moment forward, apologize to her for your behaviour. There is absolutely no excuse for mistreating someone because of your personal problems. But just because you apologize does not give you the right to continue the abusive treatment. Apologies are only if you are truly sorry and you are serious about not making the same mistakes.
Let Her Go If You Can't Change Soon
I understand that old habits die hard. If you feel that you can't make the change right away, then let her go. She shouldn't have to wait for you while you go throught this transition. Once you are over your problem and feel that you have made a significant change, than you can ask for her back.
Find Someone Who Can Stand the Abuse
However hard you think it's gonna be for you to change, just remember what you put your girlfriend through. She deserves someone who will treat her right. If you can't, then find someone else who may be willing to stand the abuse.
Hope I've Helped,