I would call the doc in the morning. Honestly rashes are very specific. What might work for one rash might make a other worse. If it's just dry skin though, maybe try a mild soap when washing and a plain, pregnancy safe lotion. But call your doctor for sure.
The other night I had a dream that a creature resembling a large sea urchin brushed against my belly and gave me an Ebola rash (Ebola rash was totally a legit thing in my dream) so my guess is that you have a sea urchin Ebola rash... But I'd double check with your doctor.
I have a weird patch of skin on my arm that is itchy. It's been there for a month and I finally remembered to ask my Ob about it. He said it looked like a patch of eczema. As pp said, skin stuff can be common during pg but I would def either call or show it to your dr when you are there so they can tell you exactly what it is!
Patches of dry or irritated skin are super normal. Try using a good, unscented moisturizer and be sure to ask your doc about it at your next appointment.
I itched my boob the other day alittle too much and it left these weird red marks, they went away a few days later, but I think it's probably broken blood vessels from scratching dry skin. If your that concerned, ask your doctor.
Re: Rash..