I was about to go for a walk earlier, and right as I thought it and started to head for the door, suddenly I got a sharp pain in my Achilles tendon that had me limping. I had to go sit down. It eased up after a few minutes, so I went for that walk. Just as I came back to my driveway, suddenly the pain came back. I was hopping on one foot by the time I got to my room. Now my whole ankle and the inside of my calf hurts, a deep ache any time I put weight on that foot. It doesn't look swollen or anything. What the heck can cause this?