I was a reflux baby, and am a GERD sufferer all my life with the scar tissue in my esophagus to prove it. Its painful, and at times debilitating. As a baby I did a lot of projectile vomiting after eating, and after being switched to so many different formulas nothing got better. I was put on solids early due to not being able to keep down formula even soy formula. After 43 years of life I can say that food is not the answer, since the reflux is still there. My grandson was born with it as well, I know the back arching, hiccups, the gas issues, the crying at all hours of the day and night, the runny acidic stools that can burn the skin, as well as the projectile vomiting and spitting up even an hour after eating.
This is my suggestion, save your DS some pain in life and have him diagnosed while DS is a baby. Yes this requires GI tubes and a monitor but you will have your answer, and with an answer comes the ability to use techniques along with medications to lower his pain level and give your son a healthier life from the start. This will also remain on his medical record for life, and save him the need to be diagnosed again later in life if it goes away and returns (depending on the severity). It will also help with the needed esophageal cancer screenings. Armed with information you can start with elevating the head of his bed (crib wedge under the mattress), reducing the acidic foods that cause him pain (reflux diet), or start him with medications that your doctor recommends. Do not just rely on one opinion from your pediatrician, talk to an internal medicine specialist as well about the diagnosed condition and screening over time as your son grows. Doing all this and understanding that if your son has this acid reflux or GERD that it Is a treatable condition and will be something he may have to deal with for life, but it will save your son from a lot of pain.