I am experiencing the exact same thing....with my last pregnancy, this "hot-bellied" feeling didn't come on until later in the pregnancy- when I was beginning to show at around 5 months. This time around, in the dead of Canadian winter, and at only 9 weeks, I am walking around with my shirt tucked unnattractively into my ill-fitting bra. I'm glad to know that I am not alone in this though and also that I'm not imagining things!