I know how you might feel Robin. I am a very careful person when it comes to my diaper wearing. None of my family or friends are privy to it. Only my wife, and my friends from here know. You might feel, only a cretin type of person will understand, and except you. At leash, except you for the person you are over and above your fetish.
OK, that being said, you also need to be honest and open to someone you think is important to you, or will be.
But, how close do you think you will be getting to this person? Do you think he is someone you want to be very serious with? Do you believe he is someone you will be with a long time?
Ask yourself, how would you feel about this person knowing your secret, if you split up? Do you think they are of good character, and would still keep your secret?
This isn't any easy question, but your answer may lay more with how much trust you think you have with them.
You may want to ask them, if they have any fetish type likes. This way, you can mutually share yourselves, and share some trust.
If you feel you are at a point where you want to have them know. I would sagest, getting to someplace privet and quiet, someplace you can talk.
Then, just start explaining what you do, what you like, maybe some of the why.
I hope some of this can make some sense for you, and maybe help you out?
I'm not an expert it this, I'm just a participant. But, I like to at least try and throw out some help, when someone asks.
If you want to ask anything more, do so. I hope you can work it out, good luck!