You should try peeing before sex. Or maybe it's not even your bladder that is hurting. Have you ever had an STI? When your pelvic region hurts that could mean that you have PID (Pelvic Inflammatory Disease). This is usually caused by an STI but also has other reasons including just bacteria causing it for no reason. You should check this out with your doctor. It cannot be fixed without antibiotics and an anti-inflammatory medication. Or maybe you have a bladder infection.