Will my sex life be affected during treatment for vulvar cancer? What about after treatment?

Probably yes. Depending on the stage of disease and treatments you will receive, chances are there will be some change in your sex life. Usually not for better, but at times it can be minor changes.
Vulvar cancer. The affect on sex is determined by the amount of tissue that is treated and whether or not the clitoris is involved. You probably have a pre-cancer not an invasive cancer at your age.
Vulvar cancer. It depends on how radical would be the treatment (surgery).