I once had frequent headaches and the internet listed all sorts of horrible diseases... Turns out I was only dehydrated and had to drink litres of water everyday...
I went on WebMD looking for advice about my stomach pains and it said I probably have appendicitis and I need to get my appendix removed immediately before it ruptures. I just ate too much ice cream.
*10 min later*
"I only have 5 days left...."