I have been masturbating last 5 years once every day and now i feel like my one testicle is smaller than other is it ok or should i consult a doctor?

It may be ok but con: It is not related to your masturbation and it may be normal but since you are concerned go consult your doctor/urologist.

Not related: One smaller testicle has likely been present since after you went through puberty. Left testicle can be smaller due to a varicocele (feels like a "beg of worms" ) or an incompletely descended testis up at neck of scrotum can be smaller ; worth consulting a urologist. However many men have one testicle smaller than other for no reason or if they had groin surgery or mumps. Likely not a problem.