At four months I just started to show, so if you've been growing out of your pants maybe you are more than two. Another thing that might be able to help is if they could hear the heartbeat, at two months, they couldn't with me, but we're all different.

If you do start getting big prego belly, or start to feel kicks, I would definately be talking to your doctor. Sorry I wish I could help more.
congradulations though and good luck!!