I Usually Have Very Heavy Flow When I Menstrate. However

I usually have very heavy flow when I menstrate. However this month it was late by about a week and it started out very light and brown and then two days after it started it got a bit heavier but still very light and the color of the blood is still a brownish red. I'm inly worried since my fiancé and I had unprotected sex within my ovulation. Is there a chance of pregnancy?