One big problem is it seems like you've been doing things for other people. You always, always have to focus on your happiness first. It's not solely selfish either. You can't ever bring true happiness to others unless you are yourself happy.
I am also considering teaching after 10+ years in corporate America. If you truly love teaching I would stick with it. IMO it sounds like you maybe went into it for the wrong reasons and now are having second thoughts. If thats the case I would look for something else that would be more fulfilling. Teaching may seem like a thankless job, and I know that this may sound cliche, but if you reach that one kid who needs help its all worth it.
