Dear B.,
Birth Control is a funny thing. The biggest thing it does is in some ways it 'mimics' pregnacy so your body is fooled into thinking it's already pregnate so it changes your cycles so you don't become pregnate. It's also not 100% effective either. If I were you I would go to the doctor, either your primary care or your obgyn, and explain what's going on to them. It's really the safest way to find out if you really are pregnate, and he will be able to tell you where to go from there and what to do, depending on what your results are. It can be very dangerous to an unborn child for you to be on birth control if you are in fact pregnate, so I would get into the doctor asap and find out what's going on with your body. It will also help with your peace of mind. I hope this helps!
S.