Well... I'm not qualified to suggest what it is you're experiencing or why it is you're thinking this way. Perhaps it's simply the result of a build-up of anxiety? However, from my perspective, this is something you really need to work through with a mental health professional. Otherwise, any suggestions you get are as likely to be wrong as they are right. And they may just make you even more concerned than you already are. Under any circumstances, there's certainly nothing to be ashamed of.

Here are links to a couple of articles from PsychCentral's archives that may be of some help with what you are experiencing:

https://psychcentral.com/blog/archiv...sive-thoughts/

https://psychcentral.com/ask-the-the...oning-reality/