random... cramps?

So it's about a week before my next period, and I'm having these weird cramp like pains in my lower abdomen. I know it's for sure not pregnancy as for I haven't done anything that could get me pregnant in the last month. The "cramps" travel from either the left side to the right side but it's almost always in the middle. I've also had a pretty emotional week and the pain has only started in the last few days. Could it have anything to do with stress? Any ideas of what could be happening to me?