I first started when I was about 12, i'd be lying in bed late at night on my ipod browsing the internet, mostly watching youtube and cartoons before I started getting curious and looking at porn. While lying on my stomach and with my dick facing downward eventually i'd sort of gyrate and use my hand to press down onto my dick until I orgasmed (I wasn't even sure if it counted as masturbating at the time, i knew what masturbation was but I wasn't cumming or doing the normal stroking method I I wasn't certain for a while)
I kept this up for a while utill I actually started cumming, at which point I stopped because I knew i'd get caught if I started leaving stains in my bed or my underwear.
Then at some point I started connecting those feelings with the ones I had about wearing diapers (cause like many people here i'd always felt weird about wanting to wear diapers without knowing why/still being embarrased by the idea) and so I managed to get ahold of some diapers, put one on late one night and masturbated into it, which was an enlightening experience because it felt like some sort of answer to questions i'd been having for as long as I could remember.