Feel like losing muscle on left. Same.

From last few months, i feel like I am losing muscle on left side of body. When i sit down, i feel more muscle in right butt and less muscle of left so I tilt to left while sitting. I can feel my right shoulders and right thighs has big muscles than left. I have left lower back pain. I feel the same from face to toe that it's less muscle. I went to 20 doctors , performed tests like ENMG, blood tests, x-rays, heart,spine mri but there's nothing. I am afraid if I will be wheel chaired losing all the muscle . When i exercised on my two legs individually, next three days , there will be so much pain only in the left leg, right leg doesn't pain much. I don't know what's happening , i feel like better not live like this, it's been atleast a year and i am feeling the same.