Sounds complicated, I can relate to what you’re going through. But I guess as you know yourself, it’s nothing you’re not able to “fix”… well rather to cope with if you love him anyway.
I only wonder, is your own urge to regress less (including everything else), or is perhaps due to him not being interested so it feels like it’s crippling your urge to indulge? Just a question, it’s nothing serious to worry about.
Besides that, I think it’s normal to lose interest partially if your desires change. So since you’re both kind of into BDSM related activities as of lately… it’s absolutly normal. Also, perhaps your little side could also be a bit bored? Figuratively speaking of course. If it’s just all the same all the time that you’re trying to enjoy due to your certain characteristics it might become boring after a while, especially if you’re alone by yourself but want to share it with your partner.
However, you’re still exploring what you may like, I still am too. My desires constantly switched some years ago and I loved to explore new things. I somehow also grew hesitated when I didn’t have to chance to try something new. Which hasn’t worked that well in my last relationship. The easiest thing which works, we mostly tend to forget about somehow, is simply communication, it’s the key in any relationship. Otherwise you won’t get to know what your partner likes or doesn’t like about individual things.
You said yourself he’s trying it in his own way, so maybe he’s just stumbling around in the dark? Since he doesn’t know better. Or perhaps he’s trying to add his own interests alongside it, but doesn’t know how too exactly. Talk to him about it, it cannot go wrong I think.
And as already mentioned, often it’s about negotiations, a favor for a favor. So even if he doesn’t like it thaaat much, perhaps he would still be eager to do it, if you also do him a favor?
Just don’t worry too much. As long as you’re happy in general it’s fine. I know it can sometimes be hard to talk about these things. Especially if you’re thinking that it’s just one silly aspect, but you can do it. That’s what your loved one is also for, to share your sorrows if you’re stuck, since he may be able to help you… no matter how silly they may be.
Best of luck hugs