Oh my god, this was me when I was pg for the third time! At my 12 week appt with the m/w, I asked her if it was normal to be so big so early, and her reply was "your body has been through it twice before, it's just popping out early because it know what it's doing".

16 week doctors appt, the heartbeat was loud and clear down the BOTTOM ( not the middle) of my belly, and I was told eveything was great, so I went on my merry way.

20 week ultrasound: TWINS!

Don't want to freak you out, but just bear in mind that it can happen.