Could I have ovarian cysts?

It's been about two weeks since my last period, I'm having lower back pain and what feels like menstrual cramps. This has been going on for a little over a week, and the day after my period, I had this really sharp pain like a cramp hit just randomly. My period seems to have ended a day earlier, too. I almost fainted the other day, and I've been queasy lately. What's going on?