Heat Rash?

I’ve Not had a rash or anything like this since I was little. I’m currently 11 weeks pregnant and since I found out I was Pregnant I have been fighting this Rash. I go see a Dermatologist May 18th and my OB had given me a steroid Pack. Yesterday was my Last pill and of course it has started to come back! This one it has spread to different place than it was before. I keep reading Articles and it sounds like a Heat Rash. It’s in the fold of my belly, the lower fold of my belly, between my thighs, behind my knees and now right next to my armpit. I’m about to go crazy with being itchy. I’ve tired Benadryl, creams, coco lotions, no smell lotions and oatmeal baths. Everything seems to be temporary nothing is long term... help me please!!!