My husband is 82 and has been diagnosed with dementia for the last ten years. He can still dress with assistance, shower with assistance, and can interact pleasantly with dog walkers, neighbors, etc. for a few minutes at a time. Lately, every thing hurts him. If he bumps his arm even sightly, if my hands are too cold, if he feels a slightly rough spot on his eyeglasses, he reacts as if it's a HUGE deal. I can't tell if his skin has become super-sensitive, or he's just looking for attention. I am with him 24/7 and he gets upset if he can't see me when I'm in another room.
It's also common for someone with dementia to become fixated on things, so that would account for some of the behaviour, such as worrying about a tiny spot on his glasses.
Being with your husband 24/7 is a lot for you to deal with. If you are able to get respite, please use it to have some rest. You matter just as much as your husband.
And your husband just wants to know that you are near even if you're in the other room, and it bothers him when he can't see you. So when you leave the room try telling him where you're going and that you will be back shortly.
I wish you well as you travel this very difficult road with your husband.