Hi, @tonnie325, you must never give up–docs who can't diagnose something and then call it a psych problem out of frustration are not docs you need. Some tips: This Mayo site has great information on it, so look up Clostridium difficile and see if the symptoms match his.
The cytotoxin test is the gold standard for detecting C. Difficile. I'm not sure, but all labs should be doing this protocol by now, but if they aren't, you might get a false negative. So research cytotoxin test (they measure cytotoxin A and B) and demand one because it might be C. Diff., given his symptoms. It could also be a FODMAP problem, which stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are simple sugars found in all kinds of natural foods and if he has an intolerance, that could make him sick in the GI tract. Celiac disease is easily tested, too.
Maybe you've tried these things, and I'm not a doctor, but getting him to Mayo would be a good call. Because he's 18 you can maybe go to more than one of the Mayo clinics (Rochester or Phoenix, not sure where else they have one). If he's that ill, it's worth getting him in if you can afford the trip. The grand rounds approach at Mayo is what saves people (multiple docs reviewing his case and discussing it). It takes time to get in, so apply today.
I know the fear and frustration you feel. You are not alone. Write me anytime here, I'll respond with any info I can share. Many moms supported me when we were in the dark woods, so here's a little candle. You can do this. I learned it helped to cry on the phone when making appointments. People want to help. Find those who can. You might have to remind them what they signed up for when they took that Hippocratic oath.