I've seen the posts you've been making but haven't replied to any yet.
First of It's so good that you are open to all this and willing to support him through it and it's great to see that you are even enjoying this new dynamic in your relationship, I hope he realises how lucky he is to have what most of us here only dream of.
I'm gonna take a slightly different angle to it though where, lots of people here and in the other threads are coming more from a "let him lead the way" kinda position, which is good and correct to a point, especially if he still seems very embarrassed or perhaps ashamed by it, you don't want to press too much or he may shy away even more.
I instead though always advocate for open and honest communication. when both parties in a relationship know where the other stands and what they feel/think, it can be much easier to move forward.
Finding some time to sit down and properly discuss things making sure to let him know how you feel, that you are sincerely enjoying it and interested in exploring and then asking how he is feeling and what he would like will give you a good foundation to build on.
He may be worried that you are only "going through the motions" and not really accepting it or perhaps he would like to do more but is worried about putting to much on you and scaring you away.
Without knowing him it's hard to really say what might be going through his head, it could be that maybe there is a lot of the AB side of things in him and he's scared that will make you think less of him or perhaps he feels like less of "a man" because of it. Maybe there are a lot of AB tendencies that he doesn't even know about/recognise/acknowledge himself. Maybe he is purely a DL and having you change him is making him feel more insecure about it, or possibly making comments about him being a good little boy or mummy changing his soggy diaper may be off putting, even if he wants that, doing so early on may feel to forward for him.
There are so many factors that can be at play, from your other posts it sounds like he may have had a bit of trauma in his childhood around continence issues. There is also the fact (and I may get flamed for this but...) that he is a man, Guys do tend to have a much more restrictive or difficult time dealing with emotions and expressing themselves or opening up.
Having a little "check in" chat with him and getting that baseline could be of help to both of you and maybe give him the confidence boost he needs to really open up about what he would like from you, and perhaps setting some limits to what you would be willing to do will give him some kind of "boundary" line so that he knows where he stands and isn't afraid to move forward worrying if he is going to go too far.
Just don't start a conversation with a line like "hey we need to talk about these diapers" that will set his alarm bells ringing that something is wrong, maybe wait until you are changing him one night, maybe before bed, and while doing it just casually and light heartedly say something like:
"I've really been enjoying changing you and having these little moments together, I'm so glad you felt you could trust me with this, but I notice sometimes you seem a little unsteady about it, I know this must be difficult for you to open up about and it's only been (a week? however long) so I thought I'd check in with you to make sure you're ok. Would you be up to chatting about it a little?"
Hopefully he'll say yes and you can sit and talk things through, but if he says no or not yet or something like that then you tell him "ok, well I'm happy to keep going if you are just know that I am here whenever you feel comfortable enough to talk about it."
That at least would let him know that you are happy, sincere and ready to accept him without being too pushy or digging into his emotional state before he is ready, it also gives him the chance to say if he isn't so happy about it, if he doesn't say anything about not being happy then you have your answer at least whether he enjoys it or not.
