Hi! My son is 7 1/2 months and he wieghs 15 pounds and his hieght is 19 inches so he is very underwieght and he is not tall enough. He eats fine but do not gain any weight and he is not talking yet which really worries his doctor. He is going through tests to find out if he has cf but it's like everyone around is beating around the bush. From what I've told you do you think that he has cf and what are the definte signs of cf? HELP!!!