LMA,
I hope you are feeling better today. I do agree with Hibee's advice on going through the self help for health anxiety from our Resources. It is free, go at your own pace ...and will bring you some relief from your worries.
The second link I believe is the longer one...full of steps to work through in order to break free from these health centered fears. It is worth you time and effort to go through these.:)
Health Anxiety - A Self Help Guide:
http://www.nhs.uk/conditions/hypochondria/pages/introduction.aspx
Helping health Anxiety
http://www.cci.health.wa.gov.au/resources/infopax.cfm?Info_id=53
Health Anxiety- The Super Scanner
http://www.get.gg/docs/SuperScanner.pdf
For now, remember how the other worries turned out...no heart issue or brain tumor, right? You have good reason to believe that this fear is also a product of anxiety and nothing more.
Wising you well.
S.C.