I had achilles tendonitis for about 3 months, and I couldn't seem to get rid of it either. I was informed by a coach to try and take Alfalfa. He told me at the time that he knew a couple of runners who have taken it, and it got rid of their tendonitis. So I took his advice, and after about 2-3 weeks, it was completely gone.
You can pick up this stuff at a GNC store. It says it's a dietary supplement, but nothing affected me. If you're willing to do that, I would strongly suggest it, becaue the results I found were amazing.