This sounds truly miserable. I understand doctors are reluctant to treat when they're not sure what their treating, but there's an old treatment for Crohn's disease that might be worth trying since the risk of side effects is very low. It's called enteral nutrition, which refers to special liquid diets used instead of other food and beverages, usually for 2 to 8 weeks to reduce inflammation and induce remission. There are a bunch of different formulas (some easily available, e.g. Ensure and Ensure Plus), and they all seem to work about the same, but some people will respond to one type of formula and not another (not predictable in advance, it’s trial and error). Doesn't work for everyone, but generally you will see improvement within 10 days if you are going to respond, so you don't have to stick it out too long if it's not working. The formulas provide all the nutrients you need in a day as long as you drink enough of the formula (say, 1800 calories per day, or more if necessary depending on your size and activity level). If you drink different types of liquids or try to eat regular food along with it, you are less likely to reach remission.
US gastroenterologists don't tend to prescribe this treatment because they think it's too hard for people to give up regular food for a few weeks, but it's a first-line treatment in Japan, and is used in Europe and Canada much more frequently than in the United States. Anyway, just a thought, since it sounds like you really need some relief from the symptoms.