What could be causing this body rash?

I have a rash that has appeared every night for the last 4 or 5 nights (I spot it when I wake up), it also reappears when I shower. It consists of small raised circular lumps (kinda like bites) and larger raised patches of all different sizes and shapes. I mostly get the small circular lumps on my face and arms, and the larger patches everywhere else. If anyone has at least an idea of what it could be it would be a great help.