You need to make sure you arch your back the correct degrees on the landing. If you don't arch enough your arms wont be able to support your body and you'll land on your head or your back, which I think is what you have been doing. I'm not sure if you are meaning a handspring in which your finishing position should be upright on your feet or if you in fact mean a walkover where you kick over into bridge, which sounds like what you are explaning. If you make sure you are arching your back and bending your legs round enough you should be able to do it with a little more practice to strengthen and stabilise yourself. If you are struggling to bend enough, gradually increase your flexibility with various exercises, but don't strain yourself because you could permanently damage your back. Hope this helped Holly :)x