I felt the first at 20 weeks, the second around 14 weeks and this one I felt at around 10 weeks. There was a post from my 1st tri. where I talked about this. I know it was the baby, it's my 3rd, I know what it feels like. I think that with you being a first time mom the odds are not in your favor, but you never know! Also, it doesn't matter if you are thin or not, you're feeling it from the inside not the outside and inside we're all the same size.