Help with Stretching

golope

I started having a tight feeling in what I think is my hamstring - a few inches below my butt on the back of my thigh toward the outside. I've tried doing every stretch I've ever heard of an all of the stretches in the P90X and Insanity DVD's. None of the stretches seem to hit the right spot.

Today when I was working out, it went from a tightness to actual pain. I had to stop and its not terribly painful now, but I feel that tightness again when I walk or sit cross-legged (indian style). Maybe just doing a lot of walking will help stretch it out? When it went from tightness to actual pain I was doing suicide drills of run, touch the floor, repeat. It was when I touched the floor that it hurt.

Can anyone suggest a good stretch that could help with this? I'm just starting my weightloss journey again and I don't want to be derailed by a major injury.

Thank you for any suggestions!