Anna, I put on about 15kgs with pg 1 and way less than that with pg 2 (and I was lighter going in second time around too). My ob weighed me at each visit and I asked her was she concerned that I wasn't putting on weight to which she always replied no.

Perhaps you could ask him what his specific concern is, and explain your history with your first pg and the fact that you are eating plenty. Then you might have some idea of his reasons and can discuss it with him further. Personally I think I'd ask not to be weighed any more as it's causing you more stress than anything. You are the patient, surely you could ask him to use other methods to determine if everything is ok. Or you could just put a lead weight in your pocket at your next visit