I read your post and was like "OMG that's me!"
This actually just happened with my boyfriend and I yesterday. He is always super supportive and I am constantly picking fights with him. I get so mean and so angry and my mind is like "what is going on?!" I have no idea what triggers it...sometimes it's just there. The I get angry at myself cause I'm so angry at him for no reason. Then the crying....
I cry after every time i have this frustratingly angry episode (which is often). I start feeling guilty about how I acting, things I said/did. It's a vicious cycle. I know it can be frustrating, but at the very least know there's someone out there who understands and is sending you good thoughts