The reality is, this is a common problem for people with big and small hands alike. Either your hands are too small and can't stretch, or they are too big and clump on the strings as in your case. I know this struggle all too well.
The good news is, it's difficult for everyone in the beginning. Using your hands in that way is not entirely natural for anyone so take comfort in knowing no matter what hand size we all start in the same place. It's simply about making it work for you, and you will. Keep practicing and it will get better, I promise.
Good luck! :D
Douglas Showalter