Re: yeast infection ?
Not sure how long elapsed between you putting in the last dose and having sex, but two possibilities spring to mind:
He's at least a little allergic to the medicine. (a lot of people are sensitive to yeast treatments, get even worse itching, etc.) Manufacturer's website boasts that, due to their "bioadhesion technology," (whatever that is) the medicine stays in the vagina for an average of 4.2 days. Since that's only the average, many women keep it in their bodies for 5 days or more.
He's actually infected with the yeast a bit, possibly from intercourse when you were just getting the infection and the friction of having sex made the symptoms start. This happens more often than you'd think, especially with uncircumcised men. If he is uncircumcised, and he develops redness and cheesy stuff under the foreskin, then that's almost certainly what's happened. Even if he is circumcised, or doesn't have white cheesy stuff, it might still be possible.
If he has it, then you both need to get treated at the same time. He would need to see a doctor, as I don't think there are any over-the-counter treatments for male yeast infections.
Or, I suppose it's possible you still had a bit of yeast by-product in you, and that irritated him. (That's why a yeast infection itches, the yeast make that white cheese, and it irritates the skin) Though I'd think it would irritate you more than him...
Might want to use spermicide-free well-lubricated condoms until this is all fully resolved, to avoid sharing anything more, whether germs or medicines.