I would talk to your doctor about being tested for cholestasis, you can google it too, kind of scary to have, I have had it once and may be getting it again this time around, and i'm 18 weeks. It usually starts late in the second trimester to early 3rd trimester, and can cause complications to the baby like still birth, and complications with labor, such as heavy bleeding.
It's caused by bile being released through your skin, I would explain it all but it's complicated which is why I suggest looking it up.
Call your OB. I had a rash from a new lotion I tried and got some cortizone cream it was gone in 3 days.
I seem to get that 24hrs after I shave my legs every single time since I've become pregnant bit drives me crazy. Poor hubby I'm not shaving my legs anymore!! But yes I would contact your ob hopefully they can give you something to help with the itching