Is a very tender belly normal??

Before I go to docs I just wanted to know whether any more women out there have the same thing.

I am 16 weeks and for the past week or so my belly (where I presume baby is) has been feeling really tender. Specially when I'm sitting down or as I stand up or when I lie on my back. It's OK to touch though and it's not painful just doesn't feel like it's normal..

Am I right to be a little worried?