I would be as open and honest as you can be about why it is hard to share about this, what you like about it, and maybe if it gets there some of things you would like to be able to do (solo or together). It will probably be helpful to explain that for many of us it is extremely hard to share this with others for a variety of reasons, that many of us barely tell anyone in our lives.
I find being willing to answer and any all questions helps, while there might be the understanding you want right away, it will create a better conversation pattern around this.
My partner is not ABDL in any way, not into any other kinks/fetishes (which I think helps some couples), but is still 100% supportive of my wearing whenever I want/need (longer story) and of being in the community (going to events).
I wish you the best and am happy to answer more specific questions if you have them.