A vaginal infection, or "colpitis", is usually contracted via unprotected sex (like an STD)... but colpitis can also be transmitted via contaminated swimming pools, toilets and baths; bad hygiene of the outer genitals, unclean underwear, etc. Colpitis manifests with vaginal discharge and irritation. Infection from the vagina can spread upward to the uterus, tubes, ovaries, parametrium and pelvic peritoneum. A common name for such an infection is a pelvic inflammatory disease. PID is a serious condition and must be diagnosed and treated properly as soon as possible.

To diagnose the cause of a vaginal infection, you can request a microbiological smear. A PAP test can also reveal vaginal infection and even identify some possible agents of cause (Candida, Trichomonas) but not as precisely as a microbiological smear. There are also specific serological tests for viruses and Chlamydia. If there is an infection present, the infective agent can be isolated and its antibiotic sensitivity can be tested. In your case, you'll need proof of any vaginal infection.

Regardless, if you are experiencing some type of vaginal infection it can’t be related with a headache. A CT scan of the head can be performed e to exclude a brain tumor. Brain tumors can cause headache and vision problems but the possibility of having a brain tumor causing such symptoms is very small. There are other, more common, conditions that can cause headache and vision problems. You can consult an ophthalmologist to check if your sight is normal, for example and to exclude an eye disorder. Further, anxiety is very often a reason for all those symptoms: headache, eye aches, ringing ears, muscle aches, pain in hands and feet, nausea etc.
There's no problem requesting a CT-scan of the head if you insist. At least the CT-scan will exclude some serious brain diseases.