Small bumps all over body that when i pick at look like a bug bite-swell up and then start to scab. painful and scab noticeably especially on bum?

Rash: While it is extremely difficult to diagnose a rash on the internet without being able to actually see it, i would be very suspicious for impetigo, which is a strep infection of the skin that can cause scabbed lesions that spread and can be painful. If this is case, needs antibiotics to clear up. If not, then need to see doctor anyway to properly diagnose, so i'd make appointment today.