Hello a lot of people would say you’re disgusting for doing that because it’s your family and it’s not normal but is anyone even normal ?
The most important step to recovery or wanting to improve yourself as a person is to admit your flaws and issues and you’ve done that so well done to you because a lot of people can’t admit when they are wrong.
I cant really say I have a way for you to stop what you’re doing but it’s clear that you know yourself that what you’re doing is wrong and you need to stop, so maybe what you can do is on a piece of paper or on your phone write down when you start to think about these fantasies, try and establish what causes you to think like this, maybe there’s something that triggers your behaviour maybe a smell or a piece of clothing I’m not sure but see if you can find a pattern. If you find a pattern try to break the cycle so if you know you only feel like this when you’re home alone then when everyone’s out of the house try get yourself out too, that way you’re not in the environment where you feel the urge to do what it is you do.
I would also advice you speak to your family about it, I can’t say they won’t judge you because the probably will because of the seriousness of the issue but one thing I do is that they will help you, I know you might feel ashamed to admit what you’ve been doing but you’ll feel a lot better when you get it off your chest and try and receive some help.
Don’t be too harsh on yourself because there’s people out there doing a lot worse but don’t think what you’re doing is right either...you’ve taken the right step in terms of admitting to your issue and asking for help so now just take another step and accept the help but most importantly speak to a family member and let them guide you. God bless you and good luck