Unknown rash...help!

I have been getting this rash for a really long time on and off. It varies but mostly it is large puffy circular rashes. They itch really really bad! They are mostly on my upper thighs and hips, but lately they have been getting bigger and showing up in more places like on my sides and butt. I started getting them about 2 years ago every once in a while but now I get them almost every day! They are awful!