What Causes Abdominal Cramping And Light Period While On Yaz?

I am on yaz, and i had intercourse after 2 1/2 weeks...I was having a little spotting before, and after, I had a lot of heavy bleeding, with some clotting, for about 9 days until my period. My period was lighter, and when I started the second pack, I had abdominal cramps. Is this normal side effects of the pill or could I be pregnant?