Gain weight!

Well today we go to the doctors appointment and they see how much I weigh and I have gained 0 pounds since I've been pregnant. My doctor told me I need to gain a pound a week for five weeks. This was a first; The doctor told me to go home and start eating candy and ice cream. Food that will put weight on me. What I'm confused is why have I gained 0 pounds and my belly looks like I ate Kalvin whole. Our next appointment is October 4th and that is when we find out what the baby is. Fingers cross its a little boy, We already have a name and its a boys name. I don't like a lot of girl names so if its a girl that is going to be a hard one.