Sharp and sudden Muscle pain between the hip and knee?

Hello,

I workout moderately, with a special focus on the lower part (walking, running, weight lifting). Three years ago, I started feeling numbness in my left leg, in particular between the hip and the knee. Every now and then I would feel sharp pain in my muscle ( I think the iliotibial tract). Every one thought it was caused by a pinched nerve, and I started doing some exercises for that purpose. It helped a bit, but the numbness and the pain kept coming back. Yesterday I was doing some grocery shopping when i felt sharp pain, like being stabbed by a knife in the muscle and I couldn't keep my balance. Within a minute the pain was gone. Now when I press the muscle with a pencil or my finger I feel the pain again. I have no bruises or internal bleeding, and there's no swelling in the area so i dont think that it is a pulled muscle. I went to several physicians and they just keep guessing and givin me pain killers (although the pain is only sudden and sharp, and not continuous), so I lost m faith in them.

Any idea what it could be?
I also have been feeling pain in my trapezius muscle (left side) and a little bit stiffness. The pain is not sharp but feels more like a discomfort when I stretch or pull weight. Not sure if the two are related.