Everyone will have a different story, so please tell yours.
My fascination for diapers came when I was around 13, I didn't knew how to explain why, but I felt myself attracted by its texture, volume and the convenience. I was brave enough to ask my mother to buy me some... and she did, she even changed me. I imagine she did this because she missed my time as a baby, since, sometimes, she said "They grow up too fast". This didn't last long, though, after two days, when I asked for more, my mom realized that something wasn't right and talked to me. She was perfectly gently and clear, and her explanation alone made me quit, she loved (and still loves) me so much.
Fast forward more than 10 years until recently. I often go to image boards that deal with a lot of fetishes, among them, diapers. I entered in a diaper-related discussion and I felt that old feeling coming back, suddenly I had the epiphany "Hey, I can buy my own diapers now. Today I have the money and I don't have to worry about my parents finding out".
When I put my first diaper after all these years I had a total blast, like no other before. An avalanche of happiness and pleasure rushed in my head, I was accepting myself, I felt secure, comfortable and complete, the next step was finding a community to share some experience.