Pain upon rising after prolonged siting?

Hello,
I would be very gratefull to anyone willing to lend their thoughts on the following. I am a 27 yr old male and for a few years now, I experence a very strange pain sensation when I stand up after siting. The pain is in the sympathis pubis I belive or where a ligament band inserts into the groin area. When this happens I cant walk witthout sever pain for usually around 15 seconds, or bend the affected area. I am an avid weighlifter but my strength dosent seem to be diminished. I did tear the same legs (right) hamstring previously, and an mri didnt help. Thank you for your time as I have been trying to figure this out for years.