You know what’s normal for you and every vulva will have its own aroma. However, fishy-smelling discharge which is thin and grey-white in colour could mean you have bacterial vaginosis, caused by a change in the acidity of your vagina. Fishy smelling, yellowy-green frothy discharge suggests trichomoniasis, an STI caused by a tiny parasite. A strong, unpleasant smell after sex can suggest vaginitis.