I also had an acid reflux problem. I had an endoscopy and my esophagus was black (it's supposed to be pink). Anyway, I took omeprazole for a few weeks, it cleared up, and it hasn't bothered me so much, but if I have caffeine or some acidic fruits like cherries, it'll come back pretty quickly.
When I smoke DMT, I also can feel my intestines do some odd things. Like soulfood, I also can hear liquid rushing around inside sometimes (for some reason). It's never created a situation where I felt I had to go to the bathroom mid trip though. Shrooms and acid are much harsher on me in that respect. They make me feel like I have to go to the bathroom (and usually won't afford me the luxury of actually being able to go). DMT on the other hand makes me go before I smoke. When I'm loading up the GVG, I might go to the bathroom 2-3 times. Then, even if I don't really go before blasting off, but my stomach still feels terrible, I'll launch anyway because DMT actually seems to do significantly well with relaxing the intestines. Any cramp instantly vanishes before I even remember I was hurting or feeling uncomfortable.