I know where you're coming from. I can somewhat relate with my condition. Whenever I see the utensil drawer unorganized, I have to keep organizing it... I keep believing that if I don't, the worst could happen. I know it's not true, but the thoughts are just so convincing to the point where you have to believe it.
Another scenario includes me overreacting about my brain. I actually have nothing worse than anxiety and ADHD, but for a peculiar reason I thought I was going to die because of a brain tumor. I knew I didn't have anything wrong with me, but then again at the same time something else kept thinking I had a brain tumor. Silly me... I ended up going to the emergency room three times to get a CAT scan, and even though the results were negative, NOOO I had a brain tumor. I literally screamed in terror, "I do have a brain tumor!!" and to this day, I KNOW I don't have a brain tumor, but once in a while I can be led to believe I have a brain tumor.
Just hang in there, you aren't the only one! Sadly I have no answer to why we think like this so much, but sometimes our minds tend to overexaggerate things, and lead us to believe things that aren't true.
Thanks for sharing!