I suffer with health anxiety, OCD and panic disorder, obsiously depression too. I'm also a psychology student. The constant checking of the mole, spot, pulse, body temperature in the presence of extreme anxiety works as an operant reinforcer (Google operant reinforcer and you will find a power point that will explain what operant reinforcement is). Basically, when you check repeatedly, it performs the opposite action from what one would like it to do and, in the long term, makes one more anxious. So you get anxious and then you check. During the formative stages of your health anxiety, when you first became concerned about your health and began to check when you were anxious, the anxiety and the checking get paired together and the checking reinforces the anxiety, making it more likely to occur at a later date.