AH my confirmation dress doesn't fit?

I would try and safety pin it. That is what I do when I have no other option. Have your mom or friend help you so you can get it where you can't see the pins. Otherwise I would try and sew it by hand just to make it fit a little better. I have a friend who staples, yes staples, her clothes when she is in a bind but I would leave that for last resort. If it wasn't a confirmation I would recommend a belt but that would cause it not to look as dressy for the occasion.