L.B.
You're not crazy! When I got pregnant with my second, I swear I was showing at 2 weeks! My husband was looking at my belly and saying, "you're pregnant." I didn't get a confirmed pregnancy test until 4 weeks later.
The body remembers what to do and just starts doing it. It's a remarkable thing!
Everything seemed to happen faster...especially the getting big part, but I didn't gain any more weight than I did with the first and baby was right on time.
Good luck to you and CONGRATULATIONS!