I am on an birthcontrol pill and i have recently had unprotected sex and monday tuesday and today wednesday i have been spotting what could it be i am hurting bad

If : If you missed any of your pills, took them late, or are within the first three packs, this could explain the spotting. On the other hand spotting can be a sign of an infectious process especially since you are having pain. Also to be safe you should take a pregnancy test; obviously if it is positive you would have previously conceived not this past week. Please see your doctor if the pain and spotting persist. Good luck.