I understand your feeling of loneliness especially after trying to explain to my wife my need for occasional escape and the consequent need for me to ensure her needs are met by arranging someone to visit every 2 or 3 hours during the day that I am away.
She insisted that she could cope and finds it insulting to suggest that she needs such support, and anyway she doesn't want "everyone" discussing" her. When I try to engage in conversation with her about her condition she refutes every observation made about her inability to undertake the basic tasks of shopping, meal preparation, domestic chores. The problem is me, who has taken over "everything".
It comes down to a very real effort to deny her condition, refusing even to consult our GP for diagnosis. It should be said that our GP has informally acknowledged that she has dementia,
Most of all I wonder how much of what I do is governed by my personal needs as opposed to hers.
Welcome to TP professor. I expect you will already have discovered that your situation is not uncommon. This doesn't make it any easier for you but you will find loads of support and information here. You need occasional escapes in order to try and support your wife. In no sense is this selfish.