Feeling dizy. Cant even drive my bike.

Before 4 months when i looked back and forth i had a vertigo .....then i had blood and urine tests .... everything was just fine..... checked blood pressure and sugar .....even that was fine ......then i consulted 3 ENT special doctors .....they said there is no problem......butfrom the day of my vertigo ......i feel lighthead daily ......i feel dizzy daily ......i cant even rotate my neck .....if i rotate i feel dizzy .. i even had done MRI of brain. ...those reports are also normal ......i cant do any heavy work nothing. ...cant even drive my bike .....but earlier symptoms were heavy but when doctor given me exercise i feel little better but i m not wholy clear ......still i didn't know what has happened to me .....i need an expert advice...