After every period, my coochie has a smell like I have bv

Everytime I finish my period I have that fishy discharge like when you have bv, so I’m always having to use bv gel to get rid of it. Anyone know why this is? I have good hygiene while on my period, regularly change my pads and only wash with warm water. I’m not over or under weight. Honestly it’s really freakin annoying because my boyfriend can tell (he doesn’t care) BUT I CARE And bv gel is not cheap.