I think Maria is "on" to something with the "if you don't use it, you lose it" philosophy. It does take awhile of regularily incorporating the new foods in pleasant/safe ways to engage your own body's enzymes. I suspect that your g.i. psychologist will help you deal with your body's terror in response to the new foods. If I'm tense/frightened when I eat anything new, then my g.i. muscles are really "tight" (constricted) and well...there's less digestive flow and often pain.
It took me about a month of regularily incorporating legumes (initially pureed/soupy) until they didn't hassle me/rattle me. Eating new foods in conjunction with familiar foods helps enormously. Texture helps too. Eat like a child and be fussy/picky! Play with it and make it fun, eye-candy to ease your body's fears. Hide something in some mashed potatoes--something challenging and new. Sneak something into a sandwich or a soup or dip or sauce.
I think, though, that keeping it very plain and simple helps a lot. Creating a calm and relaxing eating environment helps enormously. I cannot believe that I'm eating foods like bok choy and tofu and black beans and lentils regularily without attacks! Broccoli, even without Beano, doesn't give me a gas attack, anymore!
You're doing great, Beth. It takes awhile to learn that new things aren't always painful and traumatic. They're mostly different. It takes a few weeks for the body to "learn" what to do with a new set of foods. Baby steps.