Apples have a lot of fiber, but I don't think bananas do. Figs and prunes have a lot of fiber and might help you "go". Oatmeal has fiber. Salad and other "roughage". There is also orange juice that has added fiber, as well as prune juice w/fiber. Buy bread that has whole grains.
Every nutritional label lists fiber. Make sure when you make a selection between different choices like bread, you select the items that have 2+ grams of fiber.
I have to be careful when I drink too much caffeine. I don't care what they say, I have to up my water intake by 1-3 glasses to make up for the extra caffeine because otherwise I have problems.
I also take a fiber supplement (drink) every morning, and I'm very happy now. I use something called Colonix (
www.drnatura.com). It has a whole program of colon cleansing, and I did the program, but now I take the fiber every day, and you can buy it separately without doing the program. You could also try the regular ones (metamucil etc) at your local drugstore.
Sometimes certain foods are the culprit. Cow dairy products cause problems for me.