Hello. For Over 4 Months Now I've Been Having Problems

Hello. For over 4 months now I've been having problems with my head. Get pain on the right side,fairly mild. But what's worrying is that one minute I can can feel fine then all of a sudden my head feels really weiry and odd a bit like being very drunk to the point it affects how I drive etc. A lot of dizzy spells and few occasions I have passed out. Need to know what it could be.

Thank you
Ruth