early "period" on birth control

Kelly
I am on birth control and I have been for about a year now. I had experienced what I thought was breakthrough bleeding but the bleeding continued for 4 days. And I had experienced some bloating. I take my birth control every day but the time I take it varies between 12(midnight) and 2:30 am. 
I'm not sure why I am bleeding like this on birth control. I am considering taking a pregnancy test just to rule that out. 
Any thoughts and/or suggestions would be helpful....