Absolutely normal, Mellay. I was exactly the same and very surprised by it. I had expected it to be like a normal illness where you finish your treatment, get better and forget it. Not with cancer.
You will find that the obsession with cancer on the web etc will decrease but maybe it never goes away? I don't know, I'm two years out and I'm still looking! My gp prescribed a mild anti-depressant and I found that helped.
It is an aspect of cancer which is not appreciated until we have walked the path. Maybe you'd find a cancer support group helpful. Many large cancer centres focus on Living with Cancer.
Love from Helen