early period, unprotected sex, and on birth control

I've been on ortho tri-cyclen for 5 and a half years now. I stopped taking it for 2 months about 5 months ago and then started taking it again when I started dating my boyfriend. I am now on my 4th or 5th pack since I stopped taking them for those 2 months. Since I first started taking birthd control pills I never had any breakthrough bleeding and I would always get my period either on the Tuesday or Wednesday of my period week. This month, I started bleeding a week before my normal period week and it has lasted twice as long as my normal period. It is also heavier and thicker than my normal period and it is not getting any lighter. I also read somewhere that having diarrhea can affect the pill. I've been really stressed with school lately and been having a lot of diarrhea. Could this bleeding be a sign that I am pregnant? Or could it be a sign of something else that is wrong?