Why am i always thinking that i am going to have cancer.i am always needing to evacuate my bowels mostly when i get stressed. can't leave house/travel?

You need medical hel: Based on your history, I would advise you to seek medical help or counseling. If you have a family physician seek help from him/her. Perhaps he can lessen your anxiety with medication and with therapy in the form of counseling. I would also advise you to seek help to reduce your stress levels. This can be done with Yoga and daily exercise(take a good brisk walk in the mornings daily, if possible