Irrational Much?

I've always been classified as what you would call an "extremist."  I seriously go from one extreme to another - always have.

The category of "worry" is no exception to the rule.

I will worry about the most bizarre, far-fetched things on the planet.

Take this weekend for example:

I have been on several antibiotics for my pneumonia, and when I went to the doctor for my follow-up appointment last week they diagnosed me with thrush brought on by the battery of antibiotics I had been prescribed.

No big deal, I was prescribed another medicine to treat this.

Fast forward to Sunday afternoon.  I was relaxing watching a re-run of Law&Order: SVU where they were talking to a girl who had AIDS.  She went on to explain that she had originally been diagnosed with thrush, but it turned out to be AIDS.

Immediately I decide I have AIDS; at the very least HIV.

AIDS. Seriously.

And I went so far as to ask my doctor about it this afternoon.  She looked at me like I had three heads and assured me that while I did not have AIDS, the HIV virus or any other immunodeficiency disease, I also didn't even have thrush anymore.

I'm a pretty positive person, so why is it that my mind always goes to the most irrational, negative thing possible?