What can cause problems with my digestive system?

Look at diet first. Whatever goes into your gut affects what happens. Review your diet. If you aren't eating a healthy diet, it's likely you'll have some symptoms. You should be aiming for a diet high in fiber (fruits, veggies, whole grains), low in red meat (notice I didn't say none!); proteins should be lean. Drink lots of water, minimize caffeine (again,I didn't say none!). Get some exercise regularly. How's that?