We're all going through the same thing, KevinMcGovern :) I have good days and bad too. Lately they've all been good though, and you know why? I confided in my doctor, had some tests done, and was assured that all of my symptoms were anxiety. (and just so you know, I had every symptom you mentioned in your post.)
The only way you can start to get better is if you talk to someone. Finding a doctor that can work with you through your anxiety is important. They might want to start you on some meds... I personally refused any, but i have a small prescription in case of panic attacks. They can also refer you to therapy. I do group therapy which really helps change the way i think and improve my mood :) but honestly, the best thing you can do is just tell your doctor your symptoms. They'll probably just opt for some simple blood tests and if that's normal, it means you're fine, BELIEVE them and TRUST them, they are professionals and know when something is a sign of cancer. I have a HORRIBLE cancer phobia and agree with you, if i ever got a bad diagnosis i don't know what i'd do. But after plenty of assurance from my doctor and some clean tests i can feel confident (or, as confident as an HA sufferer can be, lol) that for now, what i'm experiencing is anxiety. It's a process. But we're all in the same boat here :) Please try and take some steps in the direction of learning to deal with this.
all the best to you.