NEED HELP!!!

My son is 8 weeks old and had bad acid reflux and suspected milk/soy protein allergy, and needs to have his feeds thickened. Since day 1 my son could not hold down formula, so his ped kept switching formulas. He did the best on Nutramigen, thickened w/1 tbsp of rice for every 2oz . He ended up in hospital for failure to thrive b/c of the spit up/vomiting and weight loss. They ruled out pyloric stenosis and that feeds have to be thickened so he doesn’t aspirate. He is on 24 calorie feeding. He was put on Zantac and started to gain weight. When he came home he became increasingly agitated, not sleeping and unconsolable. His GI Dr put him on Neocate (6th formula) with the rice, and his attitude greatly improved, but the reflux was constantly in this throat, and he was vomiting again to the point of bile coming up, the Neocate is thinner. I thickened it more with no improvement. Oatmeal did not work any better, so I tried Simply Thick. He was holding things down better, but he gets SO MUCH gas, he is worse than a grown man. It is hard to burp him, and he is constantly farting and twisting himself into a pretzel in pain, which is causing more spit up. I really think the problem is that he is getting too much air when he eats, I can see the air bubbles in the bottle and cannot get rid of them no matter what I do. The Simply Thick is causing the air bubbles. Now when he spits up, there is air bubbles in the spit up. I use Dr Browns bottles and level 3 nipples. I don’t know what to do, all his ped wants to do is keep changing formulas, and the gi dr is pretty much out of advice, she wants to put him on Bethanechol? to make his stomach empty faster, but I don’t want to do that since I have read it has not been studied in children. Any help will be GREATLY APPRECIATED, as I am at my wits end and have already extended my maternity leave with no pay……