Birth Control Pill & Irregular Periods: Causes & What to Do

Question
My girlfriend has been getting her period a week earlier than when she is suppose to get it. She is on birth control. She takes the pill everyday and does not miss, she is very good about it. I thought it could be something related to going back to college, and being around other girls because i heard that, that can alter a woman's period. Is it normal? And should she still follow up the week after she had her period with the week of sugar pills? Does that following week leave her unprotected?

Answer
You can't really evaluate her situation like you would if she were not on birth control pills.  The hormones alter the normal pattern and it can get worse or better than it was before.  I don't know how it effects the risk of pregnancy but it certainly is confusing.