Being in a sexless marriage through your partners choice, especially when they won't discuss it, is soul destroying. You think you've come to terms with it, but one way or another a light gets shone on it & you start the chinks. You can ask him, but sadly you can't make him answer.
IME one ex stopped wanting sex because he was very conflicted in our relationship. We were young & he knew that one day I wanted children, he'd thought he did too & it's what we had planned, but suddenly realised that he didn't. He didn't know what to do. He loved me, wanted to get married, grow old together etc just without kids, but he loved me enough to know he couldn't do that to me. Rock - Hard Place. However, he didn't make the connection at the time so didn't know why he didn't want sex anymore, he just didn't. I felt unsexy, tried all the usual stuff people suggest, turned myself inside out trying to work out what the hell was going on.
Another ex stopped wanting to...he was voted 'least likely to have an affair ever' yet he was, whilst still telling me he loved me, I was his everything and he even suggested it was a good time to start our family. He reverted back to 'at it like rabbits' for a while, then stopped again. It was like being on a bloody roller coaster. Things didn't make sense until later.
Fortunately all other ex's have remained quite steady sex wise, else I'd be really worrying 😁
However, on a serious note, no matter how much you think you've accepted it, it still affect you. Some couples are forced into it through disability, illness etc - that's hard, really hard, but not the same. It's the 'not wanting' as much as the 'not doing'.
Sometimes you just grow apart, they remain your best friend, you love them, you don't want to hurt them...but the romantic/sexual relationship just dies. Only you can decide what you can live with. Personally I think you know, but (understandably) you really, really don't want to face up to it 💐
You need to think hard about what you want to do, then talk to yur DH.
My Dad used to say 'No one told you life would be fair, or easy'