I understand why you have these feelings. I ended up in a similar place for awhile after a traumatic event. The desire to be sure it’s not going to happen again is incredibly strong.
The thing is, there is no way to know for sure that you are healthy. Any of us could keel over and die from some previously unknown or suddenly occurring problem at any moment.
You’ve already done your due diligence by checking to be reasonably sure you do not have high blood pressure. Now, you just have to let it go. When it comes to stuff like this, 99.9% sure is the best you’re ever going to do. Accept the uncertainty. It would be a real shame to waste part of the life you do have by constantly checking for something that doesn’t exist.
The best thing for your mental and physical health is to accept you are probably, albeit not certainly, just fine. If you cannot get over this yourself, I highly recommend cognitive behavioral therapy and medication as appropriate. Good luck!