I've had problems with my achilles tendon for more than a dozen years, beginning during six months of hiking in Alaska, a chronic problem with acute episodes. I have been to my doctor repeatedly, podiatrists, orthopedic surgeons, and physical therapists, all through Harvard health plans, so seeing some of the best in the world. I have had xrays and MRIs done. After an acute episode in December, when the pain was so severe my longest walk each week was down the aisle at the supermarket hobbling like an elderly man, I am feeling very good and did some serious winter ascents by late January.
Achilles tendonitis can take take months to properly heal. Oft times, three or four weeks of limited physical activity is essential to get the healing process going. This does not mean you can't exercise, but does mean giving up anything that will keep the sprained or slightly torn tendon from constantly re-aggravating itself. Cortizone shots can also be very helpful, but have very serious limitations. This winter I was surprised at how much snowshoeing and xc skiing I could do and how aggressively without causing the tendon to relapse. Biking, which I also do pretty aggressively, also seems OK. And once things feel good and my legs are strong, its back up the mountains.
If you haven't already, you should see your doctor. I have been very impressed with what good physical therapists can do--look for one that specializes in sports injuries. I have gone as often as three times a week during acute episodes, always with good if sometimes slow progress. The most lasting good advice from my multiple consultations with orthopedic surgeons was to wear very comfortable shoes(back then Rocksports were the only shoes they could advise me to wear, now there are many well-designed brands for people with foot-related issues.) with good heel support and, most importantly, to use high quality insoles in every piece of footwear, including slippers, and don't walk around without supportive footwear on. I have been using Superfeet with great success for over ten years now.
Good luck. The feeling of pain and the loss of mobility really suck. But it should pass with proper treatment.