I had a similar experience growing up. I also grew up in the late 70s and 80s. My mother died of lung cancer when I was 11, so I moved in with my grandmother. I never knew my father(he took off when I was a few months old).
Grandma was very old school and believed in firm discipline. She had a leather strap that she used to spank me when I got out of line. I already had a bedwetting problem when I moved in with her, so she made me wear cloth diapers and rubber pants to bed every night. She also had no qualms about hanging them out to dry during the warm months for everyone to see.
Once I came home late and desperately needed to pee, but Grandma grabbed me by my arm and pulled me into the living room to spank me for being late. Halfway through the spanking, I lost control of my bladder and pissed myself. She was furious and put me in a diaper right after she finished my spanking.
As I progressed through puberty, I created an attachment to the diapers. It was weird, but they really turned me on. The first time I masturbated, I was wearing a wet diaper. Similar to Joey, I would write out fantasies of diaper discipline and hide them under the bottom drawer of my dresser.
When I was about 12, Grandma found the stack of stories and confronted me about them. At first I denied they were mine, but she pointed out they were my handwriting and if I didn’t tell the truth I would be spanked. So, I confessed everything.
From that point on, I still wore diapers to bed every night for the bedwetting. However, if I did good and earned a reward, she would use diaper discipline on me. I realize calling it diaper discipline is a bit of a misnomer considering it was a reward, but it was technically discipline.
If I earned a reward, my diaper discipline would be instituted as it was in my stories for the most part. I would be diapered 24 hours a day for the predetermined time she set and the toilet would be off limits. I would not be sent to school in diapers, just at home. If we went out, I would be diapered under my clothes which was somewhat noticeable to most. At home, I would spend hours in the backyard playing wearing only a diaper, shirt and shoes. If my friends came to visit, Grandma would tell them I was in diapers as punishment for some imagined infraction. I got teased a little about it, but since shame punishments were common back then they all just assumed it was a real punishment.
Needless to say, I did my best to earn rewards. If I came home with a 100% on a pop quiz, I would earn the rest of the day in diaper discipline. If I aced a mid-term, I would get a weekend of diaper discipline. We also had an agreement that for every A I got in a class at the end of the year, I would get a week of diaper discpline over the summer. That first summer I only earned two weeks, but the following summer I got six.