No it doesn’t have to mean something, I get tight chested/weird feelings with my breathing when I’m anxious and they always get worse when I fixate on them, after a few hours without even noticing it usually gets back to normal.
You haven’t mentioned these breathing issues that I can see the entire time you’ve been worrying about colon cancer, now that you feel safe about that these feelings with your breathing are back, this is a classic cycle with anxiety and while it can be hard to break, with help you can definitely do it