Thank-you for commenting, hopefully that's the case and the pain will go away soon. I thought that could be the case but wasn't sure.
Your symptoms are consistent with an ovarian cyst. Ovarian cysts are very common and can be extremely painful at times, especially if they rupture during menstruation. However, they do not cause any serious problems, aside from the pain. Try taking a a pain medication like ibuprofen. Consult your PCP if symptoms become too severe or last for more than a few days.