Why do I take everything out on him?

I’ve been dating this guy sense january 19, 2010. He means the world to me. I would not be alive if he wouldn’t have notice how much I was hurting. I have a stress disorder, plus a bipolar disorder, and anger issues and on top of all that, I have depression. So I have a lot of problems I’m sure you can imagine. =/ My problem is that whenever I get upset…I yell at Brendon(my boyfriend) and I take it out on him. I’ve never hit him EVER. But I have yelled at him for something he didn’t do. He said he’s okay, that that’s what he’s here for. No. He ‘s not with me to get yelled at, he’s with me because he loves and cares about me and is supposed to help me. I ignored him completely for a whole day because I was angry and didn’t want to take it out on him… I felt horrible and I couldn’t sleep. I called him and apologized, he said “baby you just have to talk to me, let me in even if it hurts” I can’t do that. It’s so hard to say what I truely feel. Half the time I yell at him, I don’t even know hwat I’m yelling.=/ Plus I’m moving which doesn’t help the situation. =[

Does anyone know what I can do to make it either easier to open up and talk to Brendon, or what can calm me down so I won't yell and hurt him as much? It's killing me that I'm hurting him so much='[