Fishy smell is not a yeast infection. It is some kind of bacteria infection.
Try to change a new OG and do a culture.
If you have a yeast infection, you may feel itchy definately.
Another thing is look for a probiotic vaginal tablet, it will help you a lot.
(I know a brand of Gynoflor Vaginal Tablet)
Try to take good probiotic contains lots of species.