T.B.
K., it sounds kind of like the reflux my boys had when they were babies. They would all of a sudden start choking on mucus and we had to suction them and get it out of their throats. At least your son is able to get whatever it is out. Our ped put the boys on Zantac, I wonder if that's what your son will take? It made a huge difference for our boys and we were able to wean them off it after about 6 months and they haven't had any problems since.
It may be totally different, but my boys didn't have the burning either--they weren't uncomfortable at all--they just had those choking episodes and would also spit up.
I hope the meds help!
T.