sorry you've had such a rough time. Typhoid and E. coli, while two organisms which can cause gastroenteritis it's weird that those two were the ones you were told about ALONG with ulcerative colitis. Typhoid presents very differently than any of the E. coli diarrheal syndromes, and generally there isn't much typhoid in N. America. Unless of course you're not from here!
In any case, as long as you wash your hands well after you have a bowel movement, there should be no reason you can't be around your mom. Those bugs are only spread if you poo, don't wash your hands and then touch something that someone else is going to eat or drink.