Irregular Periods: Causes, Cycle Changes & Birth Control Effects

Question
I am 23 years old and have no children. The first day of my last menstrual period was 11/25/2005. My question has to do with starting your period early. My cycle before the last one started on 11/2/2005 and then I started again on the 25th. My cycle is usually 25 days so I am concerned. It was like a normal period for me. I am on Cyclessa birth control and recently changed to the generic form Velivet. It was the first month of using Velivet. I finished my pack of pills and started a new pack on 12/4/2005, so I do not know yet if I missed my period. Could switching do this or could it be stress?  

Answer
If you usually have a 25 day cycle (from the first day of your period until the first day of your next period) and you had a period on November 2 and then again on November 25, that would be a 24 day cycle. A cycle is considered normal if it is 21-35 days in length. YOu merely started one day earlier than usual. That is perfectly fine when you are on the pill. You were due for your next period on December 19, (if you really have a 25 day cycle). See if you get your period by December 26. If not, take a pregnancy test. However, it is highly unlikely that you could become pregnant while on the pills (even generic).