A vicious cycle: clean vagina, sex, infection, antibiotics, monistat, douche, clean vagina, etc?

Be seen. It sounds like you have a resistant infection, or something else, going on. Though i would be cautious about douching, as it has a tendency to upset the balance of the ph of your vagina, and can be contributing to this situation.
Squeaky Clean. Don't go overboard on cleaning your vagina. Don't use regular soap inside the vagina. http://www.nhs.uk/Livewell/vagina-health/Pages/keep-vagina-clean.aspx.