I have pimples in my face and in my back and i want to get rid of this. is this because of the masturbation?

Not really.: It may be hormonal, but masturbation won't worsen it. Go see your doctor and ask him for topical clindamycin.....Or try otc creams.

No: Masturbating doesn't cause acne. All young men do it; it gets you ready for marriage and fatherhood, & youth's hard enough without problematizing it. Acne on the back usually requires at least a systemic antibiotic for a man, and in addition to some topical rx you may be a candidate for one of the heavy-duty rx's only a dermatologist can write for. You have a right to a clear complexion.