Baby moving?

I think I felt my baby for the first time today. I was sitting in my chair at work and I bent forward to pick up something off the floor and when my belly squished it felt like there was a heartbeat. Little tap-tap-taps. I'm 16w2d today  and this is my first pregnancy and I was just wondering if anyone else had little feelings like this the first time or is it usually the rolling gas feeling? Was it possibly a gas bubble bobbing in there?