4 Month Hell

My son is definitely peaking in his relfux. My main concern right now is the choking. He can have a reflux episode hours after eating. They usually occur during a diaper change when he tries to laugh or make noises . He can throw up a ton of formula. During one of his episodes, formula comes into his throat over and over and he has trouble breathing. It is almost like his esophagus is spasming. When it is over, he is breathing very heavy to catch his breath and he is upset and scared. It is heartbreaking. They can last for about a minute (feels like a lifetime). Has anyone had similar experiences? I have a specialist appt tomorrow and would like any advice on whether he needs special testing. I think that it is keeping him from making noises. He seems reluctant to make sounds because when he does, he refluxes. Is this common? What should I request from the specialist? He is on a healthy dose of prevacid. I have no idea if he has a MSPI because the doctors have never mentioned it.