If you live with your parents and you're incontinent and need to wear diapers due to your incontinence then just tell your parents that you need to wear diapers because you're incontinent.
A lot of people need to wear diapers for incontinence and it's okay and you shouldn't need to hide the wearing of the diapers around your parents when you're incontinent.
However if you don't want them to know about you wearing diapers for your incontinent problem then you can just buy disposable diapers online and have them shipped discretely to your door and then sneak the diapers into your house and just wear them.
Your parents will likely not ever find out or know you're wearing diapers under your pants.
You could also hide the diapers in the back of a closet or somewhere else.