Data dog,
I think because you are not sure yet the best thing would be to go to your local community college and sign up for a class- just something you will have to take no matter what- like a science or English or something.
Then you can take advantage of their career center. Most schools have a career center that will let you take some tests for free. You might want to take a career inventory test, this helps you identify what you might like to do and what you might be good at- get a sense of how your mind works.
Another test many schools offer is a personality test like the Myers Briggs Inventory. What- you dont need a test to tell you about your personality- ok sure, but seriously sometimes I have tried jobs that are far outside my personality comfort zone and the truth is i am certain kind of person- its just the way it is and Im not gonna fight it.
Taking tests this way is better than doing them online where most are scams. But here are links to two sites- these are the quick and short versions, overall it is very broad but maybe it will help.
http://www.humanmetrics.com/cgi-win/jtypes2.asp
http://similarminds.com/career.html
a good articleabout choosing a career in the nytimes:
http://www.nytimes.com/2012/09/30/jobs/follow-a-career-passion-let-it-follow-you.html?_r=1
Good Luck!
ps I relate to your story because I know and care about someone in the same spot as you. It will not get easier as you get older. Make a change now! :)