I'm on birth control and my pills are 21 and 7 days for my period. The first 2 days of the 7 that I'm suppose to have my period, I don't! I am now getting used to that, but this week when the 2 days went by I have still not have my period!! I have NEVER missed taking any of my pills. Just wondering if it's normal to have a 4 day period on birth control??? Or why every time my period is always different?? I thought the pill was supposed to make me regular and I'm all over the place?