I have caught up on all the responses since I 'left' earlier this morning. I am immensely grateful for all of them, and some of you are really too kind. Some have been painful to read, but necessary.
I don't idolise my husband or think he is perfect (obviously!), but I also don't think he is a bad man who I shouldn't be with. Clearly, though, after such a long time he isn't suddenly going to have the eureka moment I have often wished for - the one that makes him understand me - and it's not fair of me to keep trying to have these kinds of conversations every few months hoping for a different outcome.
@Onnabugeisha I have wondered about autism at times, and it would make sense of a lot of things, but I've never been sure what good it could do me to know. I hadn't considered that different therapeutic techniques could be more or less effective in people with ASD, even though it seems quite obvious now I have thought about it. I'm not currently in treatment of any kind - after finding the treatments on offer when I was in my teens/twenties seemed to do more harm than good, I just set about finding my own ways to cope and get through the days. It has worked fairly well but obviously in only a 'sticking plaster' kind of way.
I found school and adolescence extremely difficult - I wasn't bullied and had friends, but both school and my parents had very very high expectations of me. I couldn't cope with the pressure at all, and it manifested in eating disorders from about age 14. I'm very close with my family but my mental health problems are very much the elephant in the room. I don't have any friends anymore, as I mostly ghosted them all after university. I had never felt like they liked me anyway (mostly because I knew I was having to put on a big act with them all, so I surmised that if they liked the fake me they wouldn't like the real me, because they were so different), and I always found socialising a huge exhausting struggle. When I met my husband it seemed easier to just shrink my world to be more manageable.
Logically, my husband is successful, handsome, charismatic and has friends and hobbies. He is also very capable of looking after himself, and is a great cook who kept a lovely home before he even met me. He could do better than me, so the fact that he doesn't seem to want to should actually reassure me that he must genuinely love me, even if the 'reasons' aren't tangible or easy to put into words.