Legs are heavy,rusty knees and lower back pain,can't find the problem!

Hello.
Before two year i were a soilder,nothing happend,but i just started to feel legs pain and they where heavy.
with the time my knees got a “rusty” feeling,and after that lower back pain.
now im 22 year old

right now i have pain in my legs,knees,and back.
When i going upstaries for example,every step add more ‘‘weight’’ to my legs and they become heavier.
also my knees become more rusty.

even while i sit on a chair my kness feel rusty and i have a back pain,i can’t sit without pain,i need to lie down.

I have done:EMG,MEP AND SEP(“points on maybe nerve problem”),MRI for: brain,legs,spine.neck.
everything seems fine,no problem!

I don’t know what to do anymore.which doctor should i see?orthopedic and neurologist didn’t help me.

PLS PLS PLS,someone help,give me a hint,someting, im borken.

Maybe simple xrays on your knees and leg/hip joints would provide a better answer. Possibly you have suffered musculoskeletal injuries during your time in the army.