pregnancy/Exercise ball??

Does anyone else use an exercise or pregnancy ball? I just got an exercise ball since it's cheaper than pregnancy balls and all I do is lay my back on it and sit with my legs really wide to help my hips. Any other tips to help with core or legs ? Or anything ?? I haven't exercised at all this pregnancy and I really need to. I walked a load my first and now I just don't do anything and I really need to. I can just feel my stiffness.