I am in the exact same boat as you and I sympathize completely. During most of my 20's, I had no idea what was going on. My boyfriend at the time recognized my pattern and said my period was coming whenever I started to treat him cruelly. I charted my moods and found a definite pattern. I get extremely aggressive and vicious once, sometimes twice a month, whenever my estrogen levels drop. I literally feel out of control. My thoughts are dark and terrible. I call it being in "the darkness." When I'm in it, I can't see out. I have no hope. Only agony, despair, and I feel hatred for those I actually love.
Two weeks ago, I texted by boyfriend comments about how dissatisfied with our relationship I am and how I can't go on. I said this during "the darkness."
To add insult to injury, when he called me to talk it out, I cussed at him and said I needed space. A week later, he says he doesn't think we should be together because of these reoccurring fights where I tell him mean things and say I want to leave. I explained it was my hormones talking, not me, not the real me. It doesn't matter. He doesn't want to live like this. He wants peace, he says.
This condition has ended pretty much every relationship I've been in. I'm afraid of myself when the darkness approaches. This last fight was a huge wakeup call. I'm going to see if exercise and vitamins will help stabilize my mood. I can't go on like this. I'm miserable (twice a month). The rest of the time I'm fine and dandy. I looked for actually support groups in my area but I can't find any.

I know you wrote in a few months ago but I was having a bad week and thought i needed to get on this site again. I feel for you and I can relate to how you are feeling especially the relationship issues and feelings of despair before the period starts. The mood changes scare me sometimes too cause it feels like it comes out of nowwhere and if it hits,, small problems seem like a big deal and the emotions seem out of control. Its motherf**** nuts lol. I'm sorry that you've dealth with this stuff. It seems like women have to deal with so much emotionally its crazy! I really think there are so many affected by PMDD and they think they have or have been diagnosed possibly incorrectly. Its good to have a site like this where we can turn to and vent-its necessary! you are not alone and i have used outreach hotlines when its been overwhelming. They can be helpful and have learned that they are for those dealing with any mood or emotional troubles, not just extreme stuff such as suicidal thoughts, etc. This site is a like a hotline also but it can be nice to talk in person on phone to when it is happening at that moment. Good luck and come back to this site when you need it-don't hold back. We all need strength and NEED to vent and I can be the first to tell you I do!