Bandango,
I feel for you. I too can withdraw into myself a bit. There are some days I want to go without seeing anyone, if they are nice to me I am too emotional and I know I will cry.
I have a lovely supportive husband, who can be as confused as me as to my moods, what genuinely helps me is to get outside whatever the weather and go for a stomping walk, on my own. Thoughts can then drift in and out my head, I can cry a bit (I am fortunate to live a bit rurally, so no chance of bumping into anyone if I plan my route). A bit of me time before bed to stretch and do a little yoga helps me.
Do try to find just a tiny bit of time to do something you enjoy, just for yourself. The first steps are hard, I can easily lose motivation, but just a tiny tiny step, just for you. Be kind to yourself.
I too miss me, I don't always like this me, but I am trying to accept it, some days better than others, it is hard to find a positive sometimes, being outside is mine.