Your doctor put you on THAT diet to treat your IBS???
Problem number one: Apple juice and raw apples produce excess gas and cramps in pretty much everyone with IBS. That's the last thing you should be consuming.
Secondly, bananas are constipating. You should not be on those if you are having bad constipation. The dehydrated bananas (aka banana chips--like you see in trail mix) are even worse.
There are a number of people on here who have bad gas regularly, and it moves around on them a lot. So you're not alone in that respect. Some people have been able to make it some better by taking anti-gas medicines (like Beano or Gas-X) everytime they eat. When I was having my gall bladder problems, I would get trapped gas a lot; it was like I couldn't poot anymore. Since I got it out, I have gotten some better about being able to pass gas instead of having it trapped inside all of the time. I don't know why there was a connection between the gall bladder and trapped gas, but there seemed to be.
I have read online about a product--it's supposed to be old-timey--called bile salts. It's supposed to help people who have no gall bladder and are constipated all the time because of it. If you aren't producing enough bile to break down your food, then you end up constipated; this stuff is supposed to replace your missing bile. Me, I have too much and so I have to take medicine to soak my excess up. Too bad I couldn't share with you, huh? Lol.
And have you tried some old laxative stand-bys, like aloe vera pills and prune juice? I haven't heard that prune juice causes a lot of excess gas like apple juice does, but you do have to start out on it in small doses, like any other type of fiber therapy, lest you make your gas worse. I hope your doctor didn't have you start out on a big dose of fiber all at once?
Have you looked into meal replacement drinks? Ensure, I believe, is made with soy, so it's okay if you can't handle milk. I drank a lot of Carnation Instant Breakfast drinks and Slim Fasts when I was sick with my gall bladder because they were about the only thing that didn't make more more nauseated. So long as you are not lactose intolerant, they shouldn't bother you either, I wouldn't think. And I can't imagine that a drink would constipate you!