i thought i was loosing it

about a week before my period is due i about unbearable to live with and then i get the most horriable pain in my breast that it feels like a knife from front to back. i know i'm about to get my period i told this to my dr. and he gave me zoloft it works but i get very dizzy from it the first couple days i hear there are clinical trials for pmdd does anyone know the website?