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The commonest cause of such symptoms in pregnancy
is a fungal infection
known as Candidiasis
. All you have to do is to visit a Gynecologist & let her examine you. Most doctors give treatment after a clinical diagnosis alone. This infection usually easily responds to treatment.
If it is something else your doctor will guide you accordingly depending upon her clinical diagnosis. Don't be so scarred of STDs & visit your doctor to get the treatment. You will be alright.
Wish you good health.