What Causes Bloating Of Stomach While On Birth Control Pills?

I have been on birth control for 2 years now. I just started a new 28 pack of pills and during my first week I took my pills about 3 or 4 hours later than usual. During my first week I also had unprotected sex. Now that I am in my second week of the pills, I am experiencing bloating during the whole week. I normally do not have bloating until my 3rd or 4th week. Is this normal? Could I be pregnant?