Hello and thank you for your question.
There is a fetish called infantilism that is associated with obsession about diapers. Here is a link that describes in great detail about this fetish and you can determine from reading this, if you think this is what you may be dealing with. http://understanding.infantilism.org/what_is_infantilism.php
What you can do is contact a therapist in your local area who may be able to help you to overcome this fetish/obsession so that you are not so disturbed by the thoughts and behaviors, which are obviously upsetting you.
Here is a very inclusive directory of therapists. You can do a search by zip code and read about their bios and see their photos etc. A good therapist will be able to help you with both the obsessive thoughts and other aspects of this possible fetish. http://therapists.psychologytoday.com/rms/prof_search.php
Please click the green ACCEPT button for this information. Feel free to continue the discussion with me, even after clicking accept as I want to be sure you are satisfied with your answers. Thank you.