What is wrong with me lately?

I feel like my hormones have gone totally out of wack. I've had a lot of stress the past year with my parents splitting and A Levels, but now things are starting to get better. My exams are over, the parents stuff is a lot better even though it still hurts me when I stop to think about it and I have uni coming up soon which I'm really excited about. However, I feel like something's gone wrong somewhere. My moods are literally SO bad. My mum and best friend brought up my mood swings the other day and that's when it properly hit me. The tiniest things make me absolutely furious and make me over think everything. The other day, this girl said she could no longer see me the next day due to her family coming down and I managed to get in an argument with her and delete her as a friend on facebook. It seemed completely rational at the time, but the next day I was like WHAT?! Why did I just do that? I completely couldn't justify my actions and couldn't understand myself. I feel like crying over everything and swear and use the c word when things piss me off. Even dropping toast on the floor, I shouted out swear words and slammed a door. I've been getting offended and hurt by the smallest things, like if my friend doesn't text me for a day I think they hate me. My periods have been getting increasingly worse each time since 2011 started (also heavier and worse cramps), but my moods have never been THIS bad. But they are literally out of control and I feel like it for longer (nearly 3 weeks I've been this way now). What is wrong with me? :/