Bananas always helped me stay regular, but I can't seem to stay well for very long so now they're on the no-no list again for a while. I was reading here that sometimes you need extra potassium with crohn's so it could be good for fiber and potassium for you to have a banana here and there. As far as helping you get to feeling some relief soon, that Miralax stuff is a bit expensive compared to the other laxatives in the store, but it's easy to take and it works really well once it gets going. You should also check with your doctor and let the doctor know that now you're having trouble going, when that suddenly happened to me my doctor said "Good, that means you're getting better!" I needed laxatives for a while (philipp's and miralax together) but within 2 weeks I hadn't had any problems with having to go often again, even with eating limited fiber like from fruit(yay) so they put me back on a normal diet and said to just take it easy with the fiber and not to eat too much of it.
As far as whether you should try eating wheat and stuff for fiber, I probably wouldn't do that if I were you since it might make gas/cramps since you are kinda stopped up right now. If you do ok with the fruits and get your output back to your comfort zone you could try little bits of wheat and grain fiber and make sure it doesn't bother you and make you sore or make you go too much. Hopefully you can go back to eating most of the healthy fibery foods you used to enjoy :)