I've never taken Topamax, but have taken Zyprexa. I'm not sure what could be causing your enthusiasm reduction, but it does sound like some things are improving. I hope your psychiatrist can find the right dosages to find a happy medium. Sometimes it just takes some adjustment time. Perhaps the coming of spring will do us all a little good.
That's good news that your weight gain has eased. As for weight loss, you may need to go on a diet. Topamax may not be able to do that work for you. Maybe as you find the motivation, you'll be able to embark on a weight loss program and/or exercise.