Welcome to HealingWell!
I am sorry to hear about
your ordeal will this diagnosis roller coaster. What a nightmare! I'm not a doctor, nor an expert, but wouldn't finding ulcerations during a colonoscopy mean you have Ulcerative Colitis (UC)? It definitely would explain your pain and D (and probably nausea and vomitting?). Have you had more than 1 doc look over your colonoscopy results?
Right now I'm assuming your stomach has shrunken considerably considering you haven't been able to eat. Your best bet is to introduce food gradually. Eat lots of small meals and eat healthy. Not to mention, taking a good multi-vitamin would be great for you (if you're not already). Are you on probiotics? It is so important to take after a nasty bout of food poisoning or samonella, or when on antibiotics.
going out... I would start to venture to places nearby at first. Know where you are going, know the route and know where the bathroom is there and on the way. This will always put your mind at ease. Are you allowed to take Imodium? If so, I would take a small dose of Imodium and go about
your day (out of the house).
I wish there was more I could say to help, but that is all I have for now.
Take care of yourself and keep posting.
BTW - Did you know there is a UC Forum here as well? You might want to check it out and post any questions you may have there too.