I've got something similar, mine was a pulled hamstring. Hamstrings are a ***** to heal, because they are under so much tension. The hammies need to be babied. to heal mine, I basically had to do NOTHING for about a week, so that I was completely pain free. I stopped driving a car w/ a clutch, no swimming, running, biking, or weight training. then I started stretching it lightly after a brief warm-up, and after I got out of the hot shower.

It still aches a bit when I do a really hard ride, so I take a day off if it starts to bother me, and make sure to stretch it. but its important not to stretch while you are in pain.

The PT said theres a lot of scar tissue there, since I reinjured it several times like you did. the scar tissue acts as a stress riser and so that hamstring will always be a bit weaker than the surrounding area.