Too small already

How can my pants be too small already? A pair of my dress pants is already too tight. I can zip it up and can hook the little eye hook, but cannot for the life of me get the button to work. At least I know that I am pregnant and not just gaining weight! I guess all this means is that I get to do a little shopping sooner than I thought, or what it really means is that I have one less pair of work pants to rotate. Bummer!!!!