What Is The Treatment For Irregular Menstruation?

Dear Ask The Doctor: I've been bleeding very irregularly for the past 3 months. My periods are starting around the same time each month, but they are lasting for 2-3 weeks. This current bleeding spell has been going on for about 10 days now. The flow is very light, panty liners are the only things I need. Is this a possible pregnancy symptom? During these months I have gained a bit of weight and it appears to be in the abdomen. My periods have never been this way before.