Jodie what you are feeling is a normal reaction to having your health threatened by cancer. It takes some time to believe that with treatment your body will be healthy again. I certainly felt that way and still do from time to time when feeling a bit down. As you talk with more medical staff and read more stories of other people's experiences you will loose this fear a little and feel you can trust in the treatment to get rid of the cancer.
Your view of the world has been shattered by this diagnosis but you will adjust and get some of your confidence in your health back as time goes on.
Deanne xx