Is there anyway that you can have your thyroid levels checked? It really sounds like you are doing everything right (tho I'd add more protein, too, as Jayell suggested) and you've been at this for a while.
Depression, lethargy, and insomnia are all symptoms of a thyroid problem.
The other subjective question is how intense are your workouts? If you've worked with a trainer and taught various aerobics classes, I'm assuming you are pushing yourself. 2/12 hours is a bit much, tho. If you are used to 2 1/2 hours of walking each day, your body isn't going to perceive it as exercise. But from what you've said, it doesn't sound like you're taking a stroll for your exercise.

to you...you have lot of patience to keep on program with no results.
Mel