We have been married for 33 years so YES, there have been complaints over the years. Unless he is digging back to the early years, the years of craziness of working with children going in all directions, I can't think of anything recent. I have been wondering the same thing.
He tells me it's nothing that I did but about HIM. He mentioned "my journey" a few times in our more recent conversations. He started journaling a few years ago and is in the process of writing a book. Well sort of. It seems that he's not been able to focus long enough to write as of late.
If I could get him to go to counseling, I think it might help but that is't going to happen any time soon based on his 'I'm just fine', attitude.