It sounds like you're finding out more about yourself. We all change all the time, in fact to paraphrase someone, "The only constant is change". It's fine to enjoy spending time alone or with just one other person. Society sometimes presents the extrovert position as the 'norm' when it really isn't.
If you love being in your room, doing your own thing, that's great! Enjoy that space and know that there's nothing wrong with you.
It would only be a concern if you were feeling that you wanted to socialise more but didn't feel able to do so.