I am not judging you when I ask this but "why were you practicing safe sex until recently? Once you have a diagnosis of herpes you do need to practice safe sex forever (a) to reduce your own exposure to herpes from someone else which can increase your viral load and (b) because you owe it to your partners to not expose them. Being on acyclovir is a tool to help minimize recurrences of active disease but it's not fool proof and you can have active virus without rashes or outbreaks.
It's impossible to predict the percentage of chance - just one exposure means a good possibility that you get herpes. I'd talk t him about it - see if he want to get IgG/IgM as far as testing and then go back to always using a condom and practicing safe sex.