A couple of members have mentioned using activated charcoal for the really bad gas. Most gastro doctors tell people to use psyllium fiber, like Metamucil. I have had to use other fibers, like flaxseed meal. It's true that you need to build up slowly how much fiber you use, especially when your system is obviously sensitive already. Like sparkle40, I can't use the wheat bran either. My gastro doctor mentioned Metamucil and the like to me. I told him that psyllium aggravates my GERD, so I can't use it. The naturopath said that psyllium can be irritating for a lot of people. This is why I have mentioned flaxseed meal to so many people on this site. With flaxseed meal, you can even add just a small portion of the amount you will be using for the whole day with each meal, so that you're also not eating it all at once, which might be helpful when you have such a sensitive system. Don't forget that you must drink plenty of water with any kind of fiber and with gastro problems, for that matter.
When taking fiber you have to start with a small amount and then build up. But some fibers will give you gas if you are sensitive to it. Like with me, wheat fiber will cause me gas as well as constipation. If your family doctor doesn't know more to help, see a gastrointestinal doctor for advice. They would probably do a scope of your colon to make sure all is well. I have IBS with constipation and many times I don't evacuate completely. But I don't have the clean up problem you are talking about.