Discomfort/Pressure 17 weeks: Normal?

acmayn01

Let me start by saying that I didn't think this was going to be a piece of cake :-) But I'm surprised that this week (17w, 4d) I'm starting to feel abdominal pressure/discomfort, especially when sitting. My abdomen is really just starting to show in the last two weeks, and it just feels tight and heavy, like it's sitting on something uncomfortable. It seems like it started pretty suddenly in the last two days.

I knew that this would happen, but I'm not that big (most people can't even tell I'm pregnant, I've gained maybe 5-6 lbs) and thought it would happen much later. Is this normal at this stage? Should I call doc? Anyone else having this?