For me, it is not really hamstring, it is exactly where my hamstring meets my glute and it actually hurts most when I am sitting down. The pressure of sitting presses on the spot that hurts. I went to many different doctors, chiropractor, podiatrist, and finally saw an orthopedist who told me it is bursitis. There are other factors too, but I don't want to drag out this post too long. I had a shot of cortisone to calm it down - right now it is better but he told me it may never be perfect and the pain may come back. I purchased custom orthotics to correct a difference in my leg length (right leg is 3 cm shorter than left). I just picked them up today so will start running with them tomorrow. I also got exercises from a physical therapist to strengthen my core. Good luck - this problem has been a royal pain (literally)!