Actually, contrary to some peoples belief, douching is not healthy for a woman.
A long time ago my OB even told me to never use it.
It wipes out the good bacteria which itself can cause infection so it's backwards really.
A vagina is a self cleaning part and all you should use to clean it around the area, not inside, is a glycerine soap or a mild anti bacterial soap. It's a very sensitive area so the soap you use is crucial.
The distinctive fish odor is usually caused by a bacterial infection called BV (Bacterial Vaginosis).
It is a very common infection and no, it's not sexually transmitted although the infection can be passed on to a partner even though a male is just a carrier.