Mel, it's only a number, sweetie. It could be water, it could be your scale was a little off on a weigh-in, it could be any number of things. Keep it in perspective. You're going to have a beautiful baby in a few days, and soon you'll be able to focus more on your body.
And yes, I've gained six pounds in one day, and I'm sure we're not the only ones here.

I'll bet when you weigh tomorrow, you'll be down a few pounds again.
Sending you big hugs...

... hang in there, girl... you're almost there.