Extreme itchy Rash

So I have a rash that started 24 hrs ago on the sides of my hips and now has spread rapidly from hip to hip and dipping down in between my thighs. its unbelievably itchy and red. there not like pimple bumps with a head but more like one big swollen flat topped cluster of bumps. it looks like a cluster of welps you would get from getting spanked with a belt or something. they look like welps not pimple type bumps. but more like a rash because it covers my skin. not individual bumps ya know... looks like heat rash pictures online, but nothing unusual as far as sweating. Kinda looked like hives too but my seems like nothing out of ordinary in life has changed to cause hives.

Now the rash has jumped up to just behind my arm pits more towards my back. also on one arm in the bend of my elbow.  so basically entire groin area stopping immediately where pants fit on hips, bend in elbow, and arm pits... VERY VERY itchy.. put hydrocortizone cream and took benydryl and zero rrelief from the itch... please help