fattening up my skinny baby

I saw another lactation consultant today about Chris' poor weight gain. He was 12 lb 7 oz today, which is up from his doctor visit last month, but he hasn't gained as much weight as he should have in that time period, and he is very small for his age. She had some helpful tips including a new nursing position and giving him a bottle after every feeding. I'll be doing my best to fatten him up. He has another doctor's appointment next week.