K.,
Not sure about formula in general, but if you are allergic to soy, I wouldn't overlook the possibility he is allergic.
It sounds like he is just a spitty kid (as my ped'n put it), and he needs to be upright. That being said, TALK to your pediatrician. There may be reflux involved - IANAD! (I am NOT a Doctor!)
Ask about cutting out soy and milk (milk is another allergen in some formulas; everything I've been seeing lately says no Cow's milk until Age 1. I'm not sure there is a formula out there without one or the other?
My DS had a problem with spitting up - usually a small to medium amount at the end of a feeding (or a little before) and even now he has a glitch he doesn't like: he suddenly gets a little stomach acid in the back of his mouth and he coughs. (not always burp or cough generated).
When he was that age, I had him in his car seat bucket or the swing (which sits him up). That was what the Ped'n recommended at the time - she didn't believe it was a serious problem with reflux and I didn't want him on Zantac or other drugs for something the Ped'n considered minor.
Good luck,
M.