Hey Charlie, Sorry this is delayed so long from your original post. I haven’t been on the forums in a while. I can’t completely relate to what you are going through, but as someone close to having full-blown irritable bowel, here are my suggestions.
Suggestions for right now would be to travel with people that care about you and your condition. Carry with you and only eat the food you should be eating for your condition. Be sure to bring a few healthy treats so when your friends are eating sugary food by the case, you will also have something. Also, zip locks and travel Cottonelle wet wipes changed my life in the backcountry.
As for long-term suggestions, Symprove.com, out of the UK, is a liquid probiotic that completely cured me of any bowel issues. You must follow the directions, and every morning before you eat or drink anything, take two shots of the stuff and wait 10 minutes (I wait for 12 to be sure) before you eat or drink anything else. I double the dosage when I take an antibiotic and haven’t been eating as I should. Hey, nobody is perfect. 🙂 As with all things Uphill Athlete, this is not a quick fix, I’ve been taking it on and off for several years, and it’s expensive. I wish I has taken double doses for six months or so to start. For me and my bowels and from what I understand of the microbiome research sugar is the devil for people with bowel issues. It feeds the bad biome that overruns and kills the good biome.
Anyway do your research and give it a try.
Good luck to you, let me know if you have any more detailed questions.
Brandt