How can I tell if I actually have Brain fog and focus issues or if I'm just overthinking it?

I've been feeling off and out of it for the past 3 months or at least I think so, at least at the start I know if felt worse. I fixed my diet, sleep and exercise and yet still I feel like this.

I don't know if it's in my head or not anymore, cause I don't remember how I used to feel, I find myself thinking about my focus a lot and I wonder if this always happened or if I am so hyper focused on if I'm alert that things I usually just ignore are proof of my lack of focus.

I'll admit I don't do a ton all day, cause since my focus issues I haven't wanted to, not because I can't but more so cause I want to be fully present when doing certain things.

I know I can focus sometimes or enter a flow state when I've got tasks to do so maybe I'm fine and just overthinking the general moments when I'm not fully focused.

I went to the doctor last month and had a blood test a week ago came back fine except for vitamin d being a little low, I was worried about diabetes, which it seems I don't have(makes sense I'm young and not overweight even if my diet was bad and my exercise was infrequent.)

any help on how I can figure out if there's anything wrong or if I'm just so hype focused on it that I'm getting worried for no reason