Hi Salukigirl,
You helped me with my question, so I'll put in my two cents.
I think maybe you aren't confronting your boyfriends when they do things that piss you off & hold in your anger until you "finally lose it". I can sooo relate! Sometimes I don't even realize that people do things to upset me until much later, & confrontation scares me. They probably don't think they're doing anything to bother you if you aren't saying anything. Or maybe, since you're allowing them to get away with doing whatever they are doing (I assume) which they know isn't right, they take advantage of you. More people than not will do that; it isn't just guys. I always hear that "people treat you the way you teach them to". That's why I'm trying so hard to learn how to change the signals I'm giving out, & respect myself more.
Hope this helps!