What Causes Stomach Cramps While On Birth Control Pills?

Hi I am very concerned about this. I have been experencing mild cramps just as if I am on my menestrual cycle. I am on tr cyclen birth control. And I just just started taking it this month. I had unprotected sex during the time of my high fertility period . So my question is to you am I pregnant or is it just the cramps for my menestrual cycle .I have been having mild cramps on and off for about 2 and a half week.