That happens to me, too. I just had a really bad weekend of nonstop crying. Like me, you may be suffering from PMDD, which is much more serious than PMS.
I spoke to my GYN about it, who told me the only option is to go on a birth control pill like YAZ. I've been on birth control pills in the past & found that they worsened my depression & had friends who reported the same. I declined going on YAZ b/c I'm afraid to play around with my hormones, as cancer of the female organs runs rampant in my family. And I'm glad I did, b/c it's just come out that YAZ can be dangerous. What helped me greatly was an AD called Celexa, but I had to discontinue it b/c it made my hair fall out in clumps. Don't worry- I'm very sensitive to meds, so that won't necessarily happen to you. There was a thread in the Women's Forum about this, & a few other women replied that Celexa helped them, too. Maybe you should give it a try. Good luck.