HI, THANKS FOR CHOOSING HCM, You seem to suffer from a psychiatric problem called hypochondriasis also called as health phobia or health anxiety this may be due to fear that you are growing old when you are so sure that there is nothing wrong with you except arthritis ,it means you are preoccupied with strong thought that you are ill so that even minor physical manifestations make you feel you are having a disease patient with diabetes or arthritis mostly tend to develop this situation mainly due to depression psychotherapy may be needed if you feel your feelings are getting stronger get a complete health check up done so that you clarify your doubts on your own this happens mainly when you read ,talk,discuss and know more about diseases,medications and when you surf more on the internet regarding health issues so stay cool,do proper meditation engage your self with good stuff talk to your doctor and you can prefer a psychiatrist if needed hope i answered your query feel free to contact me for further queries thank you