Period issues!?

I've noticed that my period comes more often than it should. I'll bleed for a week, off for 2 days and then bleed for a week again. And then maybe I'll be off for 2 weeks and then have another week long period. It's causing strain on mine and my fiance sex life and quite honestly has me a bit worried, and moody :/ any ideas on why?? I'm thinking maybe stress (in the process of trying to foster two little boys) causes more periods as well??