YADefinatelyNBU - of course you should find something you enjoy. I think that either having a session with a life coach or reading self-help books on DIY life coaching would be a good starting off point.
I enjoyed reading 'The Element' by Sir Ken Robinson (he's done a number of excellent videos online about education) - he doesn't really tell you how to find your element, but rather tells you about how other people found theirs. His main interest is in reforming education to help students find their element.
Have you seen the TV programme on recently about hidden talents? I only saw a couple but they were rather clever.
Back to some tips on finding what your element is, you don't have to answer them here. Don't censor your ideas in the first instance on the basis that you aren't sure how you could make a career out of them. Just write everything down and you can look over it and pan for gold later.
What do you enjoy in your life at the moment? It could be a hobby, an aspect of your work, something about your home or family life.
What have you enjoyed in the past? Have you given something up in the past because you were busy? Maybe something you enjoyed as a child/teen? What did you want to be when you grew up? Some things might be difficult to retrain in, but there might still be a way to be involved in that area of work in a more tangental way.
Imagine you are happy in 5/10/15 years time. What is still part of your life, what's changed?
Who do you admire (someone you know or someone you've heard of)? Why? What is it about what they do that's important? If they are famous, is there a biography you could read about them to explore what it is you find admirable about them.
What issues are you passionate about? Is there something you could do to raise those issues? Fundraising or volunteering for a charity, raising awareness through writing, art or political lobbying.
What kind of books/magazines do you enjoy? Is there an interest there that you could develop?
Flick through a your local college's prospectus for evening classes, part time and fulltime courses. Is there anything that catches your interest? If there's nothing locally, have a look at the OU for distance learning courses.
Likewise, keep an eye on the job pages of newspapers and make a note of any that sound interesting. You might not have the qualifications/experience they are looking for (yet) but you could get an idea of what motivates you and what employers are looking for.
These questions are just to generate ideas. Try to keep an open mind and not dismiss anything. Some people find fulfillment through their job, others in hobbies, volunteer work, family, further education etc. Sometimes people find ways of making a hobby into a small business or inspiration for a career.
You can also drill down deeper into these things and think about what you like about them. If they give you a chance to be creative, or demonstrate a skill, or communicate with people who make you feel good, maybe there is something you haven't thought of yet that would allow you to do more of these aspects you enjoy.
I don't know much about your job at the moment, but teaching is a skill that can be transferred from whatever you currently teach, to teaching about something else you are knowledgeable about - maybe by running a class or writing a book. You could look at a less dramatic change by side-stepping into a related job that has more of the stuff you enjoy in it.
My mum has taken up flower arranging and cake making as hobbies and she enjoys doing flowers and cakes for family, friends and collegues. At the moment it isn't a business, but she could take it that way if she wanted to. I think it's great that she's found a creative outlet as her job is rather stressful. I think she started off taking a few classes of these things and some others (art etc) and has kept up what she enjoyed most.
My dad is taking early retirement soon and although he didn't have many interests a while ago, he has become really into family history and has enjoyed chasing up distant relatives for information and researching in libraries and record offices as well as online. He's also looking at starting a small catering business when he retires and so has been doing a business course and researching that.
I must admit, my problem is that I have so many interests, that I don't know what I should pursue in a more serious way as a potential career, and what is just a hobby.
Best of luck in finding your passion. You aren't being at all unreasonable.