Well we don't have PMS. We have seasons.
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Football Season

Basketball Season

and some Baseball Season.

If your man is homesick, I'd say his self diagnosis tells you what it is. He is missing you or something else at home.

The only cure is time. And the occasional conjugal visit.

WRITE AND MAIL him letters.

Send him cheesy gifts.

Take pictures of you and send em.

There's not much you can do but help him feel at home where ever he is.