I have a persistent dull ache in my testicles and groin. Been to 2 urologists, had an ultrasound, no diagnosis?

The pain is affecting my life, and I haven't been able to walk long distance, which is my primary form of exercise. As a result, I've been gaining weight. I'm to the point where ibuprofen doesn't kill the pain. Its persistence leads me to believe something is terribly wrong. The pain feels like a mild kick in the nuts, or like my post-vasectomy pain.