why is this happening to me?

Yup... totally normal. You're becoming a regular guy. Nothing mystical or spiritual. We just want to watch football (or whatever) and be left the fuck alone. It's natural dude!

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.

Stop allowing people to be emotional leeches and vampires. Both in your regular life , online and anywhere else they're sucking the life out of you. Let em go buzz kill someone else with their miserable jaded asses and enjoy your life as you were meant to.

Nip it in the bud/sometimes we need company, so keep good relations with your family and friends

I have gone through times like that myself where I wanted nothing to do with anybody. It didn't last forever, although at times now, I'd rather be alone than around miserable people. I wish humanity were different, but it is the way it is, so I don't hang out with people who are negative or mean or just gossip all the time.

It's fine some people are natural loners

Depression. I had been like that the first time I was diagnosed. I want to completely isolate myself because I see them as annoying and useless piece of shits that will just tell me that it was all in my head and I should get over it.

You have darkness inside you need to sort out. Im like that sometimes.

Maybe you're traumatized by something. Talk to a psychologist

Maybe you're not comfortable with who you are.

Yet you're here.

Same. How about online peeps then? If you like us, then that says a lot. Either the people you know are not your type, or youre scared of something that has to do with being social.