Welcome to HCM.
Thanks for writing in.
the condition you are suffering can be candidiasis
,vaginal lichen planus
As it does not respond to antibiotics it is not folliculitis
As there is itching it is least likely to be syphilis .Syphilis lesions are usually asymptomatic.
A visit to dermatologist
will confirm the diagnosis and allow treatment.
A VDRL test will rule out the syphilis.
Hope this helps.
Wishing you good health.