Gaining too much weight when you're pregnant's almost entirely about eating.
Yes, you're eating for two now. That doesn't mean you're eating for *two adult people* One of those people is pretty small ;) You generally only need to add 300-500 calories a day to support a healthy pregnancy. About the equivalent of that pickle and ice cream. ;)
Sparkpeople has a whole website for pregnant and nursing moms you should check out: www.babyfit.com