Sounds like you have PMDS, Pre-menstrual Dysphoria Syndrome. It's exactly as you describe...depression symtoms get much worse in the premenstrual phase. There are treatments available. Some folks take SSRI's all the time for it. There are some marketed especially for this, such as Sarafem. Other folks take an increased dose during the premenstrual phase. Also, if you are on birth control pills, these can affect your depression symptoms. Hormones can as well. I would try talking with your GYN about this. See if you can get your thyroid hormones checked. TSH should be somewhere around 1-2. Guidelines say it is "normal" as high as 5, but for many people, myself included, that causes me to feel more depressed when it is that high. Finally, you might consider seeing a pdoc or even an endocronologist if you do not already. They might be better equipped to help you deal with this.

Good luck, sweetie.

gg