Back of my outer tights hurt when I sit for long periods of time.?

The back of my tights (mostly the outer area closest to the hips) hurt. It is in all of by back legs and as I get older it is getting worse (I am 36). The pain intensifies when I am on my period. The felling is kind of like a numbness and pain. The only time it goes away is when I am on my feet. I am 5 feet tall and I use a foot stool since it gets worse when my feet are dangling. Any advice is appreciated.