Mystery rash?? help?

So I have this rash. It started off with one little raised spot on my abdomin. A few days went by and I would notice at night my skin would get really hot like a hot flash and then it would go away. The last time this happened,the following morning it spread on the right side of my abdomin. later that night I had another hot flash and it spread across my abdomin, my lower back, legs,breast and chest.And it itches, but after I cool down it goes away some. anyone else have this around 14-16 weeks? I've heard of PUPPS but I don't think it's that since it usually happens in the 3rd trimester.