My Husband Has Heart Disease, Asbestosis, And Is On Home

My husband has heart disease, asbestosis, and is on home O2. He had quadruple bypass in 2007. He is unable to be active at all. Lately he has been getting very angry suddenly and also says that I did/didn't tell him something, when I know that I did/didn't. I have even questioned my doctor about testing me for dementia, but she said that there was nothing wrong with me. Can you help me/tell me how to help him?