toughone, but you are right, you can't change someone else, you can only change yourself. You seem unhappy; it's hard to see any way that this will change if things go on as they are (they sound as if they're slowly getting worse, in fact).
You're staying with him because:
- he'd be unhappy if you left
- your parents would be unhappy if you left
- he thinks you're just going through a bad patch (but he's the agoraphobic!)
No mention of yourself in there, which is very forbearing of you; but you do have to take your own interests to heart, as nobody else appears to be doing so. You're behaving more like his mother, devoting yourself to his well-being; and he's not returning the favour. It seems, as well as the agoraphobia, he's already becoming like a married man, letting himself go, taking you for granted, drinking, and implying that there's something wrong with you if you want to change anything.
But you are hardly doing anything wrong in wanting to go out sometimes, wishing you had someone you wanted sex with, wishing you still had your friends. I think you're entitled to a more fulfilled life than you've got now, and it doesn't look as if you'll get it while you're still with him. I know breaking up is hard to do, it always just seems easier to stay in a relationship, however bad. But your instincts are right: you need to break free. Good luck, whatever your choose.