What Causes Weakness In One Of The Legs?

hi i m gurpreet. i m 22... i m not able to walk properly. out of sudden one day my leg wasnt supporting me at all. i had all my test done bt nthng game in reports... its 4 months knw.. therapy doctor say nerve press caused this problem n knw my right leg is weak n is nt gaining strength . i cant walk nor run nor use stairs