For the last few years I have noticed I always have at least 1 pimple on my behind at any given moment, I have been told this could be from tight clothing but I can't change this as I have a work uniform 6 days a week. I need to know how to stop this happening asap!!

You can treat pimples on your behind the same way you treat ones on your face.

Not sure that you can completely prevent them, but using the same acne cleansers and medicine you use on your face will help.

Sweat will likely be present.

Use something like Tinactin anti-fungal on high humidy days.

Use an anti-bacterial soap such as Cutacura.

Use Wash n Dry towellettes when you can't wash.

Change your clothes and underwear when you get home especially when your behind is sweaty.

Sleep with out underwear.

I agree... treat your tush like it's your face. Use a cleaner, toner, and moisturize. You may want to see if some of the pimples aren’t infected hair follicles which would require it to be plucked and treated.