Hi, and welcome! I think so many of us can relate to your story. When I was in the 2nd grade, the teacher put a ball of mercury on her desk and each one of us marched up one at a time to examine it...we cut it in half and watched it roll around. This was many many years ago and no teacher would do this nowadays. Anyway, after we had all played with this poison, she says "You have to make sure you never get this in a cut or sore, as it can make you very sick." I looked down at a hangnail I had and went ballistic. My mother had to come and get me. That is the first attack of health anxiety I can remember and it continued over the years. I became aware of every strange bodily function and obsessed about it. Then computers came along and I Googled until I had everything but my coffen picked out. No more Mr. Google for me. Always the worst case scenerio pops up first.
You are not going crazy. I suggest some kind of therapy that helps you understand that anxiety symptoms are uncomfortable and distressing but not dangerous. Many of us have a fear of abandonment. My father threatened to leave my mother once a week for his enitire life and they were married for more than 50 years...it is scary, especially as a child.
Peace, and you have come to a great place for support.