My cat just had kittens.. is her behavior normal?

Well my cat just had kittens (none of us even knew she was pregnant.. she never showed any kind of signs) and there were only 3 of them.. my first concern is that I think there is one more inside of her.. I felt her stomach and can feel a hard spot where I think one kitten remains.. she keeps acting like shes about to give birth again but then doesn't and starts acting normal again.. what should I do?? and also she constantly leaves them alone and lays on the bed with me and every time the kittens cry and she's not around them she growls when she goes to them.. why is she growling at her kittens and constantly leaving them alone??