Mam’s knickers

When I was around 13 years old and my mam would leave the house I would always sneak in her room and borrow a pair of her clean white cotton panties to wear whilst I watched porn and masturbated. When I was ready to cum I would pull them to the side and cum on some tissue. I would often imagine the actors on the porno was me and my mother. When I was finished I would wipe her knickers clean from precum and put them back in her drawer. I’m in my 40’s now so haven’t done anything like this in a long time but did anyone else do anything similar. I always wondered if she knew I wore her knickers.