I think you answered your own question when you said you feel irresponsible and scared. You clearly are a person with morals, who wants to do the right thing. And not get anyone sick, on the off-chance that you do spread it to someone who doesn’t have it.
If you NEVER get sores, maybe you just need to pick the best wording and delivery, for how to tell someone. Also, if most ppl have HAD cold sores… they won’t care.
I wish you the best of luck. And send you strength for whatever you decide.
I know it’s an awful feeling. I’m in this predicament myself. And trust me, I wish I could re-do my life.