Hi H-D, thank you for sharing your story. There are a lot of similarities between my story and yours.
I've recently discovered that talking about this behavior in anyway is helpful and therapeutic too me because I've kept it hidden for so long despite leading a very normal, All-American lifestyle.
I too gain a great level of comfort and arousal from the sound, texture and feeling of security that wearing diapers brings. I am very particular about the feel (texture?) of the diapers I wear and how I wear them. I only wear adult disposable and they have to be the thick plastic-covered kind, never cloth. The brands I prefer are Secure Xplus, Cushies, and Depends. And I always wear two at a time.
Like you, I can remember being drawn to them as young as 5 or 6 years old. Later, at age 8-9 I would steal them from my younger cousin (and felt very guilty and ashamed about it).
Now my story has other aspects to it as well.
I received very little physical nurturing from my parents throughout my entire life. My parents are very good people, but they lacked in that department.
I was illegally home schooled until I reached college (talk about a culture shock) and was forced by my parents to stay home (I wanted to go to school) and lie about where we went to school. My self esteem was non-existent.
On top of that I wet my bed until age 15 and my mother would put me in different forms of diapers every night until I was 13 or 14. I've discovered through my very limited about therapy that probably has a lot to do with the manifestation of this behavior.
That was then only form of nurturing I had. And it was extremely humiliating (especially when friends would spend the night).
On top of all that I was molested by our regular baby sitter from ages 8 to 10 (when we finally moved) and was unable to get up the nerve to tell my parents.
Once or twice a month she would watch my brother and I at night. This required her to help me put my diaper on at bedtime (my mother didn't trust me to do it alone). While doing this she would rub my penis either before or after she put the diaper on. Around the time I turned 10 I began to ejaculate, which was terrifying. She would then tell me I was disgusting and spank me until I cried.
I hid this until last year when I finally told a therapist for the first time (it felt great to get that off my mind after 30-plus years!).
After we moved I continued the behavior as best as a I could. When I was 15 or 16 I would buy diapers at the drug store (very secretly) and that has continued to this day. I keep a supply in my attic.
This obsession has led to many problems with relationships and intimacy as you can imagine. I've been married for 11 years and my wife has very limited knowledge of it. She has found them on occasion and I've to tried (and failed) to explain it. We rarely have sex and when we do I am petrified I will disappoint her. I have never achieved an orgasm during sex, but am able have powerful and frequent orgasms while wear diapers.
I want more than anything to please her and have a normal relationship, but this compulsion is way too overpowering. I'm afraid I may never find a solution, which I why I'm on this site. Therapy may speed up the process, but it is difficult and frustrating because I haven't been able to find anyone knowledgeable about this.
This site has been much more helpful so far. For example I'd never heard of a transitional object until now.
Anyway, that was a mouthful and any feedback you, or anyone else, can provide would be greatly appreciated.

Thank you