English Trainer Chronicles: What do women get every month?

Last week.

Me: "I'm not feeling so well."
Female learner: "Why?"
Me: "I'm having a difficult time with... you know, the monthly problem of women."
Learner: "I don't understand."
Me: "What do all women get every month?"
Learner, oh-so-matter-of-factly: "A paycheck."

This week.

Same learner: "I'm not firing on all four cylinders."
Me: "Wow, where did you get that expression?"
Learner: "My (British) bf described me this way when I told him about our lesson last week."