I might add here that I'm not suggesting anyone divulge their diaper fantasies after they're married. I was married in 1973 and that was a very different day and age. Homosexuals were put into mental institutions against their will just because they got "found out". African Americans recently won the right to integrate schools. There was no internet, but there was a lot of hate and violence. I had my life threatened in 1971 just because I had long hair. So divulging that you enjoyed wearing and using diapers and fantasizing about being a baby would usually land you in a mental institution. My mom sent me to one in 1970. It was difficult enough telling my wife before we were married, that I lived an exclusively gay lifestyle all four years of college.
Part of the problem is that there is almost nothing in our society and more importantly, the media, that depicts how societal fringe people lived in the past. Even now, we have the idiot show, The Real O'Neils showing how much fun a gay high school kid is having in school, being out, a far cry from the kid in the movie, "Moonlight". Acceptance has not come easy: not historically. Those of us who went before all you younger members paid a price for paving the way for the 21st century, and as we all know, it's still far from perfect.
Yes, you should tell your SO about how you may express yourself sexually, but also expect rejection and having that bit of news circulate among your social group. That's what people do.