No you shouldn't be worried. Everyone shows differently. I am just 7 weeks now, and even though my tummy is a little thicker, I don't have a bump. With my second I did start showing right away though. And with my first I didn't show until about 5 months. Each pregnancy and each woman is different. It is hard somtimes though, you want that beautiful bump, but remember at 37 weeks, you will be not wanting that bump anymore. So know, it will happen soon, and probably all of a sudden.
I also suffered servely from heartburn with my second pregnancy. I wish you luck. It wasn't fun, if I remember what I did to help it I will tell you, but I can't remember now
