If you are in that much pain then you need to see a doctor or go to your local GUM clinic as soon as possible.
They will probably do a smear test and have a quick look at you. Dont worry, this will be fine as long as you relax and will only take 2 mins, will be over before you know it.
I had something similar a while back- cervical inflammation- which basically meant that I would get deep pains and severe bleeding after sleeping with my bf. A course of antibiotics sorted it and Ive not had any problems since.
If its not that, Im sure they'll be able to find the problem for you. Next time you sleep with your bf, try changing the position and see if that helps.