Im 3 1/2 month pregnant and my stomache isnt hard at all?

For my first pregnancy my did t grow until the last two months. For my first and second pregnancy my belly didn't begin to really fill out and become hard until about the 5th month. In fact, I am 7 1/2 months pregnant now and up until about the 5th month I could suck in my belly mostly and it would appear flat if I laid on my back at 3 1/2 months. It's completely normal, don't worry : )