Jax has been referred to a pediatric g.i. specialist at Children's Hospital. They are looking at appointments for next week. I've received many great tips/advice from all of you and I've written them all down. I'll be speaking with the pediatrician again tomorrow about the upcoming appointment as well as some of the advice from you all.
He seems to keep his food down decently well if he's laying belly down on my chest while I'm sitting up. So as long as I have a helper at the house for Brady, I can hold Jax like that for the 2.5 hrs he requires to keep the whole bottle down. I'm going to try sleeping on the couch with him so I can sit up with him in that position while I "try" to sleep and tube feed him slowly. His feeding process is now about 1.5 hrs long in order to get a bottle to stay down. He was weighed today by the home nurse at 5 lbs, 5 oz. He hasn't gained a single ounce, but he has maintained his weight at least. The nurse called Brady a "truck" and he weighed in at 8 lbs, 8 oz. She weighed him just for fun since he no longer gets in-home nursing assessments.
So far the doctors/specialists/nurses do not think Jax has a lactose intolerance or any allergy problems to his medications. If he had any of those things, he would have bloody/loose stools, and he would not "feel better" by a certain feeding position. He has classic severe reflux symptoms for a preemie of his size. He is on Lansoprazole (Prevacid) that helps a little with his reflux pain, and I think the g.i. specialist is looking into a medication for his vomitting. We will be able to rule many things out with the g.i. specialist. The only other medication he is on is a diuretic for his lungs.
Here's a few pics of the boys today (please ignore the vomit stains all over my sweatshirt!)