I agree with the others, say the previous infection has come back.
Other option: sneak the antibiotiocs into his cuppa. Quite a few, you know, just to make sure.
If he's previously been treated with them, he won't get an allergy or something.
A word on the side though, can't help saying it though I've done many a wrong things in prev relationships, too: don't sleep around without a condom. Imagine what you could have caught!!! It's unfair on your partner -if you don't care about your own life.
I feel sorry for millions of partners out there who get infected by chlam, HIV, HepC, etc. because their partners didn't care.