Oldwoman, so sorry you are feeling so down at the moment, but as most folk have said, be kind to yourself, but if it doesn't lift, please go and see your doctor.
I think, as we get older, our friends/family/colleagues and so on, diminishes for various reasons and we find ourselves more and more alone with more time to fill and it can lead to these sort of feelings.
Joining a group with people who have similar interests can help to get you out of the house and may find you a good friend.
It is hard though, have been feeling similar myself recently for no real reason, but I know I have depression, so keep telling myself it will pass.
Hope you feel better soon xx