Hi

I think is not only hamstring strain, i think Your pelvis and/or lumbar back is involved in this problem.Possibly between the last lumbar and the first sacral level, or/and ligaments of the pelvis, or /and Wikipedia reference-linksacroiliac joint. Is important to invastigate it, cos imbalance can hinder recovery of your hamstrings, or be the source of your problem.
thanks
take care
get well
Jarek
Fizjomanual I Fizjosport - Start