The thing is OP, you say that all the acceptance and the changes etc need to come from him and that you need do nothing.
But in reality you also say that you had a good sex life until you started feeling these bouts of tiredness, and yet you’ve done nothing about that.
Certainly you shouldn’t feel that you are obliged to have sex with him, but equally it’s not just a case of you deciding that you have no sex drive and that all he has to do is accept it.
The truth here is that if a woman posted that her partner no longer wanted to have sex with her after they’d previously had a healthy sex drive people would still put the onus on the partner to do something about it. And if the reasons were because he was tired then people would say that he was being unreasonable if he at the very least didn’t seek some help for his tiredness and that the OP wasn’t unreasonable for feeling rejected.
I am the one with the non existent libido in my relationship after having previously had a very healthy sex life. The reason is because I developed a serious heart condition and am on some pretty hefty meds which kill my libido dead. Added to that, by the time I get to bed my blood pressure is shot,I am knackered, and on a couple of occasions sex has left me breathless and feeling absolutely dreadful. As a result me and DP have maybe had full PIV sex five or six times in the last two years although I will do other things for him on occasion.
And while my DP absolutely accepts no as a response, there are times when this frustrates him because we went from a healthy sex life to virtually nothing overnight. And as much as I know he should accept “no” as an answer,I also need to acknowledge that while my sex drive has dropped, his has not. And while there are absolutely reasons for this to have happened, this doesn’t make him feel any less rejected when he knows that previous intimacy is now just going to be pushed aside because of my needs iyswim.
So we have talked, and talked, and talked,and sometimes we haven’t agreed because he wants to be with me and me saying no feels like rejection, and to me his asking feels like pestering even though it isn’t meant to be. But ultimately we have had to end up on the same page in terms of the reasons and the way forward, otherwise there would be no future for the relationship.
The answer needs to begin with two-way communication. And while that means that he does need to listen to your reasons for not wanting sex, it also means that you need to be able to acknowledge how always being rejected makes him feel. Only once you can both empathise with the other can you move forward.