Yes talk to the dr first. I called my dr all the time and they were very helpful.
My two sons had trouble after eating. They were having difficulty with breastfeeding so we had to go the formula route. My older son seemed to be lactose intolerant (so is his daddy) so Soy worked immediately for him. My second son seems to be allergic to milk protein we tried soy, pre-digested formulas (Emfamil etc), then we had to go to Nutramigen. Nutramigen is hypoallergenic. We also kept him upright for 10-15 minutes after eating to help him out. Some gas-ex might help too. Gripe water is a natural or more natural anti-gas drop.
I hesitate to put a baby in a car seat only because I did this with my older boy when he had RSV to help him breathe (on a RN's advice in the hospital) and he vomited up his formula. I had to tilt the entire carseat forward to make sure he didn't choke or aspirate. I didn't waste time trying to get the straps open. So I, personally, don't feel comfortable with them in any seat when sleeping. But you can also tilt the entire side of the crib up where his head is or put a pillow under the mattress to tilt the mattress up. They just tend to slid a bit
. They also have pre-digested soy formulas now too.
My mom suggests you roll him. We put the baby on the bed and roll him over (stomach, back, stomach etc) back and forth across the bed to help move the gas. My husband's technique is to push the legs up like a catcher and push down the knees on the tummy. This has produced some loud gas passing in our youngest and helps him get more comfortable.
Hope this helps!