I used to get thrush evey month about when AF was due. Supposedly it can occur when the acidic environment in the vagina changes with your cycle.
I sent DH to the Dr to get checked out.The Dr told DH that it is a common misconception that men can keep reinfecting you with it, dunno if I believe that.
This is what helped me.
I make sure that when I shower that I don't soap up too much as soap strips away natural fluids which changes ph and thrush can multiply rapidly.
All the lacy gstrings got the chuck as the nylon keeps your bits warmer than cotton and thrush grows in warm environment. Also tight jeans went too.
Take acidophilus tablets like Kelly said and eat yoghurt.
Get onto it ASAP. I kept a reserve of canestin just in case as even a few hours can make the differance between a hideous case and a not so bad one.
Sorry don't mean to lecture just want to help as I know your pain!