I know what you are going through. I suffer from GAD and health anxiety is my big one at the moment. Do you dwell on a certain illness or part of your body, then eventually move on to another 'illness'? like, worry about brain tumours then the month after worry about heart disease? Or is it germs and catching something that bothers you?
Try to look back on all the health worries you have had, and how many of them have turned out ok. Most of them?
Now, i have a friend who did have testicular cancer a few years back (he is now 100% fine) and i mentioned my health worries to him. He responded, that in all the time he had cancer the VERY worst thing was the unnecessary mental torment he put himself through, imagining his own death over and over, obsessing over the illness. He said his biggest regret is that the anxiety wasted so much of his life. Now he says, he doesnt worry about ill health so much, for every minute you spend worrying you may as well actually have a disease - for the amount it affects your quality of life. He urged me to let it go, live for the day, and let it all go. He reminded me of a basic truth - worrying doesnt help, it makes things worse. Easy to say i know!
His story affected me deeply, and though i still worry about health, i try to remeraber all this. You have to be strict with yourself i think, mentally give yourself a shake when your thoughts turn obsessive. Remeraber that negative thoughts cause anxiety, which clouRAB your thinking even furthur. Its a hard cycle to break.
Would you consider something like hypnotherapy? Its very good for this sort of problem, and you dont have to talk, drag up the past or make much effort at all! Worth a try?
Try and take some positive steps with this. For instance, nstead of googling symptoms, google 'curing health anxiety' or 'postive thinking' or 'mind body natural healing'. Or make an appointment with your doctor about whatever problem you have, then sit back knowing that you have taken the best practical step and there is no need to think of it until the appointment. Give yourself permission to relax.. take a deep breath, exhale out the worries, and try to think of something pleasant instead.
Tell yourself this reiki healing principle each day as an affirmation
"Just for today, do not worry"
Best of luck