I fantasize fat girls n my wife is skinny hence no sex drive and ed. how can a psychologist help me. as m not able to get satisfied with her sexually?

Skinny vs fat: It sounds like you're making it your wife's problem [being 'skinny'] that you feel "no sex drive and ed" with her. A psychologist or sex therapist might be able to help you understand that there's more to sexual attraction than the shape or size of one's body. Was your wife heavier when you first met her? It seems you have plenty to discuss in therapy, and perhaps your relationship could grow.

Fantasies: I'd suggest consulting with a sex therapist.