Will the cancer affect my sex life?

Depends. This really depends on what type of cancer you have and the treatment that you will receive. For example, if you have prostate cancer then surgery or radiation can result in erectile dysfunction. It is also possible to have psychological issues related to a new diagnosis of cancer or treatment that can impact your sexual health.
Depends on cancer. If it involves prostate it may..But chemotherapy or radiation therapy for any cancer can make you fatiqued. Depression is also possible with a diagnosis of cancer and makes an impact on many every things including your sex life.