Rash!!!

I'm 37 weeks and I've developed this rash around (10/27). It started on the back of my right knee and eventually spread to my shin and then to my other leg and now it's slowly going up both thighs. It gets itchier than normal if I bath/shower or at night. I haven't changed soaps, lotions, or detergents and my water isn't too hot. I even tried switching to different soaps to see if that helped. And it's only worse. I've never been one to develop skin problems (only one in my family that doesn't have any). Anyway, I googled a few things and I think I've freaked myself out more than anything. My next OB appointment is Tuesday (11/3). What should I do??