Achilles tendonosis

I will try to keep this short.  It's been 5 years since I injured my achilles tendon in my left foot.  I was rushing to work one day and thought I would do sort of a speed walk so I wouldn't be late.  Out of nowhere I felt a sharp burning pain at the back of my ankle and that was the start of problems for the next five years.  At the beginning I would take ibuprofen, stay off my feet and ice it and spent most of my walking time wobbling to take pressure off the left side.  Eventually as time went by, the burning pain only came when I was standing or walking for more than 2 hours.  Staying off my feet relieved the pain and it never hurt when I was sleeping and flash forward 5 years and I am still having a hard time walking/standing up to 2 hours and if I do the burning pain returns and I feel a tightness from the bottom of my heel all the way up to the calf.  When I am sitting i sometimes randomly feel an electric shock or tingling by the tendon.  I've had acupuncture with electricity, Graston deep tissue massage to break up scar tissue, and doing the stretch exercises.  I recently had an ultrasound and MRI and everything looks normal.  They did an EMG(sp?) to see if I have a pinched nerve but that came back normal.  So what could be wrong???