What Causes Foul Smelling Vaginal Discharge During Pregnancy?

Hi I m 16 weeks pregnant I have been checked for std s which all came back negative, since just before I fell pregnant I had a horrible smell down below which was very fishy, I shower daily and change my underwear daily but over time this smell has got worst and now the skin around the top of my vagina - near my clitoris is very itchy and the skin is peeling, it s not sore when the skin peels but it s very annoying. The itch does tend to be worst at night time.