I too have this, with hypochondria, your thought feed your symptoms, the more you worry, the more your sympathetic nervous system goes into 'fight or flight' mode. This releases nor-adrenaline, which binds to b-adrenalergic receptors, increases heart rate, causes you to panic more, heart pounds, which send you into a panic attack.
Go to your doctor, tell him about these symptoms, he will most likely prescribe you with Beta-blockers, probably 'Propanolol', this will make panic attacks impossible.
Go to a psychiatrist and request CBT (cognitive behavour training), this will help divert your thoughts.
Good Luck