Many people in life spend too much time worrying about what is right or wrong, what is normal, what is not. And others spend a lot of time trying to tell others what is right or wrong, what is normal, what is not. And then many people do as they damn well please.
I would not be guilt driven if I liked diapers, and really, in the big picture what difference does it make. Everyone in life has kinks and many are fun. My take on all of this is if it hurts none, then what difference does it make.
To pacify things at home, maybe you can work some compromise until you eventually get your own place and then you can do as you want. To me, therapy for this is silly and a waste of time, and only lines the therapist's pockets with money. Believe me, there are far worst things in life. If you like it, do it, but to me you just need some kind of compromise for now. Your parents well might never come to accept it, and often that's just the way it is.
I'm gay and I've had to endure stupid crap in my life, don't let them get to you, as I mentioned, I think you just need to compromise until you eventually get your own place.