Just need some insight

So I’ll apologize in advance for this may be a bit long.

So, my fiancé and I have been together about a year and a half. Newly engaged. Anyway, recently he has been acting just less interested, never mean or anything. Just seems kinda, meh? Idk if it’s just the “honeymoon” phase has wore off or what. We have been living together about 6 months now. He’s always been sweet and loving. But he’s also quiet and reserved. I don’t know if it’s just all this COVID crap and just all the emotions that have came w it or what but he just seems to be disinterested. I don’t know what I could have done for him to act this way. I know he isn’t cheating or anything like that, but I decided to ask him the other day if he was still happy w me. I think it caught him a little off guard. He gave me a weird look like why would you ask that and said yes he was. Then I asked again the next day just to make sure. He said “Yes generally” asked what that meant and he said it means stop asking and he wasn’t in the mood. He was also at work. Which can be stressful for what he does. Anyway, he’s not one to express his feelings (like many man tend to be) I just don’t know if it’s me overthinking or what but I love him dearly and it just doesn’t seem to be himself. He also hasn’t been getting great sleep, which I know can contribute. Just idk what the deal is.