Hi @mrscords,
All of your feelings are completely normal for any sane human being. The diagnosis shock then active treatment is a hell of a wallop to a person. Any counsellor will tell you it's good to cry when you need to. I'm a year on now. You've come to the right place here. In this post-surgery stage, it's really important to do those exercises for your arm - to prevent cording or tightening of your arm and shoulder. Just gently.
Learning more about your diagnosis may ease your anxiety. I read these books lent to me by my lovely GP (if you don't already have a great GP, find one):
Breast Cancer, Taking Control
DCIS of the Breast, Taking Control
both by
Professor Boyages, MD, PhD
Director and Professor of Breast Oncology at the Macquarie University Cancer Institute.