One way to make progress in your training efforts is to spice up your methods. I try to expand my "fitness toolbox" as often as I can by learning to use different types of equipment and modes of training. Often, doing something out of the ordinary will propel you out of whatever sticking point you might find yourself in. In the fall, we are blessed with one of the best natural strength-training tools you'll ever find.
I'm talking about the pumpkin.
Stay with me here. A pumpkin can be used the same way as a medicine ball would be, and has the same practicality. The only drawbacks to pumpkin training are that eventually the poor pumpkin rots after several weeks and you can't slam or bounce a pumpkin like a medicine ball - unless you like the idea of being covered in pumpkin guts!
As far as size goes, select a pumpkin weighing approximately 10 to 20 pounds for most women, and 20 to 40 pounds for most men. Get a pumpkin that has a nice round shape so it's reasonably easy to handle.