Does anyone know what this is??

Every time Im on my period I have symptoms of a yeast infection eg. Pain during sex, itchiness and burning but thrush treatment doesn’t seem to clear it up. It started when I had the contraceptive implant in my arm, I have now changed to the copper coil due to other problems with the implant but this problem hasn’t gone away. I’ve been to the doctors about it quite a few times just to be told it’s thrush and given treatment which doesn’t help🙄does anyone have a clue what this could be or what’s causing it? it’s really affecting my relationship and my confidence as I can’t be intimate with my partner until it clears up which can take time.