Could I be? Please Help.

Recently every time my boyfriend and I have sex it's been sort of painful. Like at first it hurts like crazy then after a while it lessens to where I can actually deal with it and when it's over and everything it hurts like crazy again. Then a few minutes later the sides of the lower part of my stomach starts to cramp up.. We've been having unprotected sex for a couple of monthes but I took birth control and recently decided to finally try to have a baby. I've heard of people getting pregnant while using birth control and I know it's possible.. I'm just wondering what could be the cause of these pains. I want know if it could be something bad or if it's a symptom of pregnancy.