Does anyone know what causes boils in the vaginal area during your menstrual cycle?

Every month when I get my period I get these painful boils on my vaginal area.They only come when my menstrual cycle comes along. The other day I had one that was so big and painful that I had to pop it. when i did that a purple-ish looking discharge came out along with some white chunks of other stuff. It totally freaked me out and I'm not sure what to do. has anyone had/have this problem if so what should I do