I have been feeding my 20 week old DS and since 8 weeks old he has been gaining only about an oz a week, sometimes losing weight. I went to doctor with him as he looked very thin and he had lost 6oz in a week. He is now the same weight he was at 8 weeks old. Doctors advice was to give up breastfeeding. I want instant weight gain and see that as the only realistic option. I did a 'top up' today and now he wont feed properly at the breast, as if he is expecting a bottle. Any advice?