Warning: some tmi ahead

As I've mentioned on here before my body has... trouble digesting food... at the best of times. My body also reacts horribly to stress. Right now I'm six weeks out from the biggest exam of my life, and my body has gone into "unable to process food" overdrive. I've had constant heartburn for the last couple of days any time I eat anything, been super nauseous, and somehow managed to spend even more time than usual in the bathroom with terrible diarrhea. I know, I know, I should see a doctor and I will... after my exam or if this gets worse. I just have gone to the doctor so many times with these issues, and they'll test me for a million things and they all come back normal, and my school health center is just soooo bad. What I'm really asking for is suggestions. Right now I'm eating nothing but rice and taking a ton of tums, but if anyone has any suggestions for non-offensive foods (because I also need to stress eat) or things I should do other than keep taking tums, I'm all ears.