I want to stop physically abusing my girlfriend

I have anger issues that have worsened over the years because I've never dealt with my emotions. My anger has never been expressed physically until the past year. My girlfriend has had to endure these episodes. I love her, and I think I'm about to lose her, if I already haven't. I throw things at her when I'm angry, and sometimes I hit her. I may not hit her enough to cause harm, but I still physically lash out at her. I don't want to lose her, and I don't want the situation to worsen. I am a lesbian in my early 30s, and I have been dealing with anger since my childhood. I'm ready to change. I need help now. I'm about to explode.