why is this happening to me?

You just need some me-time for yourself to collect energy so you can socialise yourself again when you have overcome this time in your life. We all need such moments.
However it could also be that you are HSP as I am. That is short for 'high sensitive person'. It means that sometimes I can't handle being with anyone and I HAVE to be alone. I already work by myself which I enjoy so much, but when I come home I simply HAVE to be alone in my room for at least an hour. I can't stand company many times because I get easy overwhelmed by the energy of other people. I used to think 'energies' are fantasies and science fiction, but it isn't. even none-HSPers can pick up energy from other people who are feeling bad and knowing everyone on earth will always be dealing with SOME sort of problems, it makes perfect sense to want to be alone to keep your inner peace.