I think this might be temporary, brought on by overwork or stress. Teaching is like acting. You have the same part each day - sometimes you get a new role - but the delivery doesn't change much and the repetition can grind you down. You must have felt this way before and then come out of it. There is also the pressure of performing well and getting results; but maybe I am wrong and you have just run out of steam. You wouldn't be the first or the last. You could try another sector or, as you seem to be suggesting, get out all together. I am surprised that you are so worried about this as there are plenty of opportunities out there to retrain - just look around you in the college in which you teach. The solution has been staring you in the face. If money is a problem, then perhaps you could retrain part-time while you still earn as a teacher.
Dilemmas should be emailed to Donald Short at firstname.lastname@example.org