Here's a website I found useful:
Calorie Calculator - Daily Caloric Needs
twisniewskikozak, maybe try to mix up your activity and your calories. The body doesn't like when things get predictable; it adjusts. The website above gives you a place to put in info; maybe your calories are too low, or read about the zig zag calories and see if it's something you might want to try.
Maybe change to walking, biking, jogging, something besides the dvd's, just to mix it up a little for the stubborn old metabolism?