NTA, you always inform anyone you’re sleeping with if you’re having sex with other people, especially unprotected, while you’re with them. And you don’t say you’re STD free if you don’t actually know. He lied to you and to this day doesn’t understand that he was wrong for putting you at risk, so while it is in the past, you have the right to be upset with him as long as he doesn’t acknowledge his wrongdoing and apologize. The mindset of “well nothing bad happened so it’s fine” is dangerous, and I wonder what else he might have done or will do in the future with the same justification. It might not be so “harmless” next time.