I have tons of pimples on my back. what can i do to get rid of them?

Serious Rx: You've already got scarring. You need to start with topical benzoyl peroxide to affected areas as tolerated and get seen by a competent physician who can supplement this with prescription meds; topicals won't clear disease on the trunk. The oral contraceptive pill, spironolactone, an antibiotic, or something else will clear you.