Did you eat something before your workout? That always helps me avoid feeling tired and ill. As Donna mentions, it could just be because you were at the end of your workout and were more fatigued. Try doing those at the beginning of your workout and see if it's better for you.
I literally fell off the darn ball last Friday so I can relate to the title of your thread.
Personally, I hate the stability ball, but I imagine it's because my core muscles are weak so I have a hard time on the ball. I did one set of three reps on the ball and one on the dome (after I fell off the ball, my trainer put me on the dome--lower to the ground so safer!
), and I was out of breath and drenched in sweat.