Is there something wrong with my son?

[moodywren]

My 9 month old son is still only having one small meal a day, about the size of a baby yoghurt. If I try to increase it he just throws the whole lot up. My health visitor told me to get him checked out by the GP but I was hoping he'd grow out of it as my GP always give me the impression he thinks I am paranoid.
My son also only does a poo once a week, is this normal?