Sorry to hear you're having troubld :(
What exactly do you mean when you say you can't eat fiber? Are you saying you can't eat a certain kind of food (e.g. wheat bran, vegetables??) Or a certain kind of fiber (insoluble or soluble)?
Knowing what you can't eat could help me give you better advice. The primary way I try to manage my symptoms is by controlling what I eat. With that being said, I think that is would be practically impossible to cut out 100% of your fiber intake since soluble fiber and insoluble fiber exist in so many foods. It would also be unhealthy to do so. I am sure that in your soft foods you are taking in some fiber, probably in the soluble form which is much more soothing on the gut.
Other than diet, I have found the best ways to manage my IBS symptoms are through reducing stress, getting plenty of exercise, getting adequate sleep, and taking a flavonoid supplement. I was on probiotics for a long while, but am currently giving my body a break. I have also just accepted that there are times when I am just going to have really bad days no matter what I do. Rx medications for IBS didn't do anything for me. I take Imdoium about every 2-3 days to maintain stability. I'm also going to start therapy again to try to get my anxiety under control as it can play havoc with my IBS.
My mother has IBS, and she's found that one of the biggest things she can do to help control her symptoms is drink lots of water. Any day that she doesn't drink enough water, she's in agony.
I hope you find a diet that helps!