It's just something that turns you on. I have the same problem. I get erections when seeing diapers or wearing diapers too.
It's not the person in the diaper that turns me on but it's the diapers.
Women turn some men on and diapers turn me and you on. There's nothing wrong with it. We're just wired different.
If we were all the same the world be a boring place. You're not alone in your feelings.
Although you have to be 18 to become a member there are a few websites you can browse and join up when you're 18.
The 2 Adult Baby Diaper Lover forums are
http://adisc.org and
http://dailydiapers.com/board