I may have a similar problem with pain on the back of my hips, mainly after sitting. I think it's called the SI joint. For me stretching, Elephant Walks and Elevated Foot Hip Flexor. I do both of them each morning and had gotten some progress. After bitching enough to my chiropractor, she is has also start making progress on it, note: she has another title, SWMBO, She Who Must Be Obeyed, my wife, hahahaha.
I'm a lot older than you so mine could be different.
Who ever you have look at it, make sure they understand working with athletes, most doctors don't. I'm lucky in that my gym has a PT in it and my wife worked on IFBB body builders. So both know that "Stop Lifting" is not an option.
Good luck in your search for a solution.