Hi! I was diagnosed 3 years ago, and have lived with non-GF roommates pretty continuously throughout. I also had vomiting & weight loss problems prior to diagnosis. I also had a lot of anxiety problems prior to diagnosis, which sounds a lot like what you're experiencing now.

I don't think I've ever cross-contaminated myself, or been cross-contaminated by a roommate- it's usually dumb mistakes at restaurants, conferences, or other outside food situations (ex: fajita maker shared between flour and corn tortillas, my italian grandma baking bread everywhere, drunk me ordering nachos from a food truck). These suck, and you should be careful to avoid them because if it happens too often you'll have malnutrition issues again, but being glutened is also not the end of the world- you'll have ~ 3 days of puking and sadness and recover. Now that you know what the problem is, you won't ever be as sick as you were pre diagnosis again. I'm not recommending throwing caution to the winds here, but it's harder to poison yourself than you think it is. Gluten cannot penetrate ziplock baggies, so just put your fruit in a box or a bag and be happy :)

Have you actually had vomiting episodes again after being diagnosed? If yes, and you're eating 90% granola bars and toast, the problem might be 1) You're allergic to something else/have another health issue, 2) Your anxiety over cross-contamination is making you physically ill, 3) You're eating 90% granola bars and toast, so your stomach is super confused. I think it would definitely be worth mentioning your anxiety over this to your doctor.

It also is very socially overwhelming in the first few months. Grocery shopping was so stressful for me then, and so was eating with other people. It really does get a lot better- my close friends understand my issues and are very careful and supportive about what I can eat, and I'm experienced enough with it now to be careful around other people.