Whole body rash of clear pimple like bumps that cause severe pain/itch, I've only had it twice in 2 yrs and it lasts for roughly 2-3 hrs... Any ideas?

Possibly miliaria. If the bumps only last a few hours, they might be miliaria, which is temporary plugging of your sweat ducts so that the sweat collects in the skin in tiny blisters. Miliaria can be very uncomfortable--sometimes it's called "prickly heat." you can avoid it by staying cool and dry.