This sounds similar to a problem I had when I was training for an uphill time trial and was forcing my body to do more than it was ready to handle. My PT was able to work on it, but it required DEEP tissue work on the lower section of my calf. That is seriously painful stuff, but it was effective though I'd try to avoid it. I tried Lamaze breathing techniques and he still made me yell out in pain. lol

If this sounds similar, try backing off a bit. On a steep hill that often isn't an option, but I find that you don't necessarily need to "attack at 100%" with each pedal stroke. If I back it off maybe 5-10%, overall performance improves since I don't tire as quickly.

Good luck.

Bob