Are you female?
I had a fibroid tumour - I've never had kids and have quite a bit of muscle, but I still looked pregnant. No other symptoms except feeling bloated sometimes. I tried dieting as i had put on a few pounds in weight, got to the point where I looked gaunt and felt ill, then went to see Dr. Nearly too late.
However you feel, go see the GP and tell him what's up. It maybe something, it maybe nothing. It's better to act early than ignore something. Prevention is better than cure. That's what the GP is for.