Something isn't right. Really - we should only get thrush down below if we either get 'low' in ourselves, or as diabetics (or the undiagnosed) we have too high BG for too long.
Two choices here - either see a doctor that specialises in those bits (ie a gynae) OR take yourself off to your local GUM. Yes! - what people referred to as 'VD clinics'. Not ALL the patients have had iffy relationships you know. Seriously, they haven't. It's the place to go, expert help for all sorts of things, TV, BV, VA amongst them - and there are very specific treatments for all of those - let alone anything else they deal with.
I'm wondering if you actually have TV instead? -
http://www.nhs.uk/Conditions/Trichomonas_vaginalis/Pages/Introduction.aspx
I have - twice - yet I'm a serial monogamist - and it seemed VERY like thrush both times. Thing is - they take a swab every time - results for common stuff are back within the hour so you just sit and wait - but more intricate stuff takes a couple of days.
So whatever you have got, will be identified properly rather than giving you a broad spectrum (though appropriate for some things) AB - you'll get the orrect AB instead, which should actually work. Some of the stuff is passed back and fortch, so both of you need the ABs - and that's important cos your partner in crime may have absolutely no symptoms.