[37M & 28M] Need advice on navigating an ADHD/Autism dynamic

My boyfriend [28M] and I [37M] have been together for almost four months. While we're still very happy, the honeymoon period is over. That's fine and natural, but I'm a little worried about how I'm handling a few specific things that are starting to bother me.

He's autistic, and I have ADHD (primarily inattentive). This has been an incredible point of connection for us. And yet, some of his behavior, most of which is related to his neurodivergence, is grating to me. Worse, it's less the behavior than his lack of shame around it.

I think that the issue here is pretty clear: I'm projecting because I was diagnosed late in life and forced to hide who I was without realizing it. I've learned that being openly neurodivergent is "unsafe," and have gotten extremely good at masking because of it. Basically, watching him be himself triggers me. He was diagnosed at a young age, and his generation is generally more well-versed in mental health, so masking just isn't something he does all that often. That's incredible.

He's done nothing wrong. In fact, part of my issue is probably that I envy him, too. It should make me happy that he's comfortable enough around me to be his authentic self, and it does. I want to be that safe space. But my nervous system responds to this behavior as danger. And while rewiring this response is my life's goal, it's real work that's taken years of intentional self-reflection to get where I am today, so I know how slow-going progress like this can be.

To make things a bit more complicated, some of his vocal stims and behaviors are actively at odds with my own needs. For example, he'll get stuck in a loop saying the same thing over and over again while we're co-working at his place, and because I struggle so much with focus, I feel like my brain is on fire.

I told him I felt this way and that he doesn't have to do anything differently, but that I might leave the room and put in headphones, and that it's nothing personal if I do. He completely understood, and I intend to keep doing that so he can be him and I can be me. This is part of what I really love about him: he's mature enough for me to say this and not let any ego get in the way. That's rare and really lovely.

I don't want to change him because, well, I don't want to, and also, I can't. I can only change myself. I know that and intend to do so. I am completely comfortable talking to him about these things, too, but I also don't want to be that guy who's always "talking" about the relationship instead of, you know, just being.

So the advice I'm looking for: if you've been in a similar situation, what changes did you make to feel more like you were accommodating yourself without dimming someone's stimming? Something similar to the headphone thing that doesn't involve him at all — just something I can quietly do to take care of myself if I'm feeling dysregulated?

I like this guy, and my discomfort is not his responsibility. I just haven't navigated something like this before, since most of my past partners have been either neurotypical or more in line with how I present my neurodivergence.

TL;DR: ADHDer diagnosed late in life looking for self-soothing techniques to handle autistic boyfriend's behavior without shaming him or myself in the process.

I appreciate any help you can provide. Thanks, Reddit!