T.H.
My acne wasn't as far down, but I had acne on my back so back that my husband fondly referred to me as "lizard back" behind closed doors. Sweet, huh?
My OB said there wasn't much we could do, nightly lotion rubs helped relieve the itch, much to my hubbie's dismay. Since it wasn't painful, I just lived with it. I would call the OB office and have it looked at - it could very possibly be something treatable, and wouldn't you like to be able to sit at some point in your pregnancy? ;)
Best of luck to you!