Tricky, this, mainly down to lack of detail. Still, I'll take a swing at it. If I miss, hey, everyone strikes out once in a while. So buckle up, this is gonna be a long one.

You ain't angry at him, are you. Sure, he does something - or doesn't do something - and that sparks your ire, but it isn't his fault. It is 100% yours.

"Victim blaming MM? We thought better of you!" the collective mutter goes up. In this case, kinda.
I am not blaming the questioner for being abused, and, as always, anyone in an abusive relationship has my utmost respect and admiration for getting the hell out.

You haven't left your abusive relationship yet.

It is still right there in your head at all times, tainting everything it touches.

You got stuck on the anger stage of the five stages of grief (which apply equally well to a dead relationship as a dead person). It is a way of protecting yourself from that crap ever happening to you again. A very seductive and comforting way, that lets you feel in control. Feel a little power in your life.
Beware stranger. Rage can become a habit, like everything else. An instant, automatic and drastic response to anything that even mildly ticks you off. Meaning in this new relationship, you are the abuser.

Yeah, payback's a b*tch.

Enough of the explanations, lets grab the toolbox and get this thing fixed, right?

Firstly, if you have not already, or even if you have, you tell your guy. The whole damned sorry story, start to finish, with nothing left out. Budget an entire evening for that at least, and yes, he is gonna ask questions. Probably a lot of questions, and some of them will pound on your rage buttons like a furious gorilla with a rock.
You will scream and you will cry. Expect that. Think of it as the pain that comes with lancing a boil. Hurts like hell, but you can't heal without it, and it lets him know there is a damned good reason for him frequently being struck by lightning from a clear blue sky. I mean, most guys are pretty laid back, but it has got to be baffling him.

Next is one word. Control. Yeah, the tricky one. It is down to you to control your rage. Not him, not me, not anyone else. When you feel it come bubbling up, close your eyes and count to ten.
Use the hand trick - again close your eyes, make as tight a fist as you can manage. Visuallize all your anger pouring down your arm into your fist. Then open your fist wide and throw that crap away.
Sounds pathetic - but it works rather well, not only for controlling rage but for really scaring cashiers.

Thirdly, no drink, no drugs. OK, it may not apply to you personally, but it will apply to others reading this. The very last thing you need right now are substances that blunt your control and magnify your emotions. Yeah, the temptation is there, but take it from an expert in that particular brand of stupidity. It don't work at all.

Fourthly, look at your boyfriend. Really look at him. Engrave every pore, every hair, the little patch he always misses while shaving - the works - into your mind. That is not the guy that hurt you so badly, is it. Why should he pay?

Finally, take some alone time to talk to yourself and get to know yourself again. You still got a long way to go to the acceptance stage. What happened to you was foul - I ain't gonna minimize that. Yet it happened. You cannot change that. You also can't move on until you accept it.

One final thing, as this is turning from an answer into a freaking novel:

Don't be scared.
It's gonna take a while and it is gonna hurt, yes. Won't lie to you about that.
Once you have handled it though, you know something? People can't remember pain. Sure, you remember something hurt, but not how much.

Good luck.