Infant vomiting

My LO is 1 month old now and still has yet to get back to his birth weight. Starting out at 5.15 and dropping to 5.5 as of this past Tuesday. He has had a lot of trouble with throwing up when he eats even though we burp him frequently. He started out exclusively breastfed and didn’t have trouble with vomiting at the breast, but his pediatrician wanted us to bottle feed breast milk and add rice cereal to encourage weight gain. (Yes I’m aware of the dangers of rice cereal. We use it for a day and I quit because his vomiting got severe). Anyways, since quitting the rice cereal we have done one ounce of breast milk and one ounce of Enfamil Enfacare which has extra calories to help preemies to gain weight. He started out doing great but now has started throwing up nearly his whole bottle.

I called my pediatrician and he suggested trying infant oatmeal in his bottle which I refuse to even try. All I want is to help my son gain some weight so we can go back to exclusively breastfeeding where he was doing the best 😞 I just don’t know how to get him to stop vomiting so much. We do his feeds sitting up and angling him upright, as well as burp him after every half ounce. I’m just at a loss at this point and beyond frustrated!