How do I know what my purpose or calling is?

You cant and wont miss Gods calling for you, the only way you can do that is to sin and turn away from him. If God wants you to do something he will put it in your heart and it will bug you till you move towards it. We are given alot of choice, he could have 16 different roads for you to go along which will all get you to where he wants you. You said your self you are a recluse, this is fine but you have to get out sometimes, join something, a church? do something to meet people. As for work, work is good for you, keeps your mind active, helps you meet people, gives you money to spend, it has heaps of benefit, if your worried about work, start with some thing casual? Work your way into it, try find something that you could enjoy, maybe even volunteer some where, get some skills. There are lots of places you could volunteer and that will help people. It sounds like your being a bit lazy, go out and do something or you can only blame yourself when your not happy with your life, God wants you to have everything in abundance, but he cant give that to you if you just sit at home and feel sorry for your self.