Extreme weakness since 5 months.

Since last 5 months, I am having extreme weakness that my legs and body starts shaking after walking a little or climbing up stairs a couple of times even. I feel numbness of legs, arms and weakness throughout the day. I get legs pain quite often. The pain is just like we get in the fever or like after extreme workout.When I check, fever is never there.sometimes the body temprature is even below 98. I have got almost all the tests done and all tests are normal. HB,thyroid,typhoid,cbc,vitamin d3 and b12, calcium, electrolytes, liver function test, lipid profile,wheat allergy. All of them are normal. I have taken several multivitamins even and my diet is normal too. Please suggest me the way out. I am not finding the way out and am completely hopeless.