K.W.
hi--I have 2 boys of my own and they both have tended to do things in stages. First they would eat a ton then they would not but they would sleep a ton. This is still going on with my youngest-he was 1 in Aug. I think as long as he is gaining weight and not losing it - he is on the right track.
If it makes you more comfortable -- call the doctor's office and you can talk to a different doctor or a nurse on the phone. I know you said that they said it is ok but if you want to get another opinion for yourself there is no problem in calling.