Oh my gosh, congratulation to you!!!! What an amazing thing to fight through cancer! I hope you really acknowledge how brave that is. Some people give up and you didn't and succeeded!
It sounds like you are doing better mentally, but please don't hesitate to contact a therapist if you don't feel back to your normal self soon. I'm actually a therapist (I know I know, a therapist on an anxiety forum lol) and it is extremely common to go through what you did in relation to anxiety. And I think I may have a different take on what your previous therapist said. We NEED to feel we have some control over our own bodies. When we are told we have cancer we basically loose all of that. It is left up to medications and treatments and dr's- and it is a total feeling of powerlessness. It has nothing to do with you being cocky etc, it has to do with you went from taking control of your body, working out, eating better etc, and one dr's appt made that all vanish. At that point you didn't even know if you were going to live through this. How could you not have anxiety? Unless you are a robot I would think it would have been impossible.
If your are still bothered by your symptoms at any point I would highly suggest seeing a therapist that specializes in EMDR. It is a type of therapy that deals specifically with trauma and it works very well. When someone tells us we have cancer we are traumatized and don't know what the future holds. We fear pain and death. All of this causes symptoms. For some, those symptoms pass with some time, and for others they last way too long. Like I said, it sounds like you've been doing very well, but if you at any point feel like you you haven't come as far as you like, definitely seek help because you deserve to be cancer free and anxiety free!!! Congrats to you again!