Am sorry u r having so much trouble feeding ur son. Patience and persistence keep trying, feeding him whenever he wants and try different things. I would also recommend Pediasure that help my son to gain weight or mix his milk with Nesquik or other flavorings. Just whatever u do do not try to force him to eat because then for sure he won't eat. Best of luck
I would get a new doc or ask to be referred to a gastroenterologist and/or allergist. My son was my biggest baby at 9lbs 4 oz. he had trouble gaining from the beginning and was considered failure to thrive. He fell off the chart by the time he was a month old. He refused all bottles, all formula. Would only breastfeed, and did so every 3 hrs around the clock. He still wasn't satisfied. He would scream, arch his back, pull away during feeds. I got referred to a gastroenterologist finally after all my persistence. Then an allergist and dietician. He was only taking in 40-50% of his calories. He is allergic to dairy and eggs with a slight wheat and peanut allergy. He also has reflux. Ended up getting a ng tube for feeds and it was the best thing we could have done. He currently has a strong med for reflux, ng tube for night time feeds(as he finally started accepting a bottle and hypoallergenic formula during the day), takes in 90% of his calories, and is only a pound away from being 50th percentile for weight according to his height. All huge accomplishments in about 3 months with lots of hard work. He will probably have to do feeding therapy too as he is weird with certain textures. If your gut is telling you something isn't right then it probably isn't. Keep insisting until you get referred or get answers. Or get a new doctor! Good Luck !