Hi, Helen !
Have you talked to your doctor about your recently IBS flare up ? If not, you should start with your doctor. I know that when I started eating more fresh fruit and veggies, the extra fiber did seem to "clog" me up. However, that was short term. I can't remember how long it took for my body to adapt to the extra fiber, but before long, it did.
You might ask your doctor for a referral to a dietitian who specializes in IBS. They could craft a nutrition plan that would make sure you're getting all the vital nutrients your body needs, plus lose weight.
For now, have you talked with any other members with IBS ? You might join one of the IBS Spark Teams. You may find talking with other members who have the condition helpful. www.sparkpeople.com/myspark/groups_individ