Why do you have a white substance on your ear drum?

I'm not a medical expert, but it sounds like you may be describing cerumen, which is more commonly known as earwax. Cerumen is a waxy substance that is produced by the glands in the ear canal. It helps to protect the ear from dust, debris, and other foreign objects. In some cases, cerumen can build up and become impacted, which can cause hearing problems, pain, or ringing in the ears. If you are concerned about the white substance on your ear drum, you should consult a doctor or other medical professional.