Hi, and thanks for your medical question on eHealth's Ask a Doctor forum.
The white-head pimples on the vulva around the clitoris and urethra are probably genital warts which is a STD. If you have a history of unprotected sex or a leaking condom then this is the possible cause. The other STDs which should also be thought of are chancroid, syphilis, molluscum contagiosum, and venereal warts.
The other possibilities are allergy to something that came in contact with this area like soap, power, undergarments etc. It can also be a vaginal fungal infection, which does not itch initially. Simple bacterial infection, atopic dermatitis and some forms of eczema too can cause these symptoms.
It is difficult to comment beyond this without examining the lesions. Discuss these possibilities with your gynecologist. Hope this helps. Take care!