Not so much that you have nothing better to do.
Rather, that if someone not only becomes the center of your world, but the WHOLE of your world, it's going to enable dependency and the kinds of things you're experiencing. Loneliness enables dependency. It was pretty easy to guess just from this one post that this was likely part of what was going on.
Having friends around also means that other people who care for you can call you back to earth when you're clearly going deep end.
Plus, okay sure: having something to do besides sitting by the phone? Helpful.
No intimate relationship is helped when one or both partners don't have full lives outside of the relationship, other friendships, other aims and goals. So I'd start by seeking out some new friendships if all your old friends have parted. Get out, on your own. Nab a very part-time volunteer gig, where you can do something you care about AND meet some new people. Talk to people in your classes, go to meetups. Et cetera.
And do yourself and your relationship a break: when you have the crazy paranoia? Write it down, don't bring it to your partner. And if you need solid plans, not something casual? Then ask for a commitment to a time and place: if you can't get it a given evening, then you don't need to commit to being home either.
In a word, reclaim your own life, for yourself. I assure you, it'll make a huge difference.
[This message has been edited by Miz Scarlet (edited 01-14-2006).]