Soy is known to cause stomach problems maybe stop and see if the pain subsides
Soy is for sure something you don't want to overdue it with. And eating too much of anything can be bad for you and can even cause your body to become allergic to it.
I'd cut soy out completely and see if it helps. You can still get good protein from fruits and nuts, as well as other beans. Or, just go get some vegan protein powder.