Non-Healing Wound on Leg for Almost 17 Months?

I have had a non-healing wound on my left lower leg. It is around 10 cm long and 4 cm wide. It started out by getting stitches in my leg. The incision became infected and I had around 7 surgeries to get rid of the infection. I then was left with a wound vac covering the wound. I had a 3 skin grafts to try to heal the wound and when the plastic surgeon performed the skin grafts he cut out my suture marks so that it would be one "pretty" scar without surrounding suture scars. All three seperate grafts failed leaving me with a bigger open wound. I have gone to SEVERAL doctors including a wound specialist, which I see once a week, a dermatologist, a infectious disease doctor and many more. I have had 3 PICC lines and 1 central line so that I could have IV therapy. No one is able to figure out why my wound will not heal. I am a healthy 20 year old female who has ALWAYS been active and athletic. Does anyone have any ideas? I am sooo sick of CONTINUOUSLY hurting. My pain ranges from a 6 to 10 on the pain scale. I have been referred to a pain management doctor because the pain medication I have been taking all this time does not work as well anymore. Which leads me to also ask what do I expect at a pain management doctor? Thank you!