What Causes Unbearable Pain During Intercourse?

I have been experiencing pain whilst I am having sex. It is sometimes unbearable. I have troubles passing urine for a few says after intercourse. I have seen my local gp and she put a finger up me and I was sweating and in alot of pain. the doctor said it was my cervix and diagnosed me with pelvic inflamitory disease (PID). I was given medicin which didnt work. She was unsure if I had PID as she said there was really no way to test this. What is wrong with me??