I feel the same way too, P.C.
Do you have a local rec centre? They might have some ball classes.
When I was at the gym, I took the afternoon ball classes on Fridays. OMG, does she ever work it. The next day, my glutes, arms, everything is aching and sore!!
One of my fav excercise for the core is to hold the ball in front of you and then squat. And to add more flavor, twist the ball to the right and then bring it back down to your left.
What are your trying to focus on, P.C.?