Who just left the flatshare ?
On this site you'll see quite a few flatshare ads which read something like. 'Looking for somebody with their own friends' or conversely 'we don't want someone in our flat who eats their meals in their room.' This usually refers to the person who just left. It isn't reasonable to expect your flatmates to be your friend and carry you. Often this just happens anyway, but it shouldn't be expected.
If really didn't want to flatshare, spending all your time in your room can be REALLY disturbing for the rest of the flat. This always causes tension in shares, and the people that do it never understand why.
If you find yourself rehearsing your rights i.e. 'It's my RIGHT to be in the property because I've paid for it, then you are either in the wrong flatshare or you need to live on your own or with your partner.