Hello,
First of all vaginal itch can be due to allergic reaction or contact dermatitis to your undergarments, sanitary napkins or tampons, soaps etc.There is no change in the colour or smell of discharge in this case.
Secondly, It can be due to vaginal infections or STD’s like Chlamydia or thrush(red,sore,itchy vagina along with pain during sex and slight increase in the vaginal discharge may be present), Gonorrhea(Itchy, red, or swollen vagina and Pain during intercourse, urinating or abdominal pain may be present),Trichomoniasis(red, very itchy vagina along with greenish, frothy discharge is present) or Lichen sclerosis which is a non-infectious inflammatory skin disorder which affects the vulval and perianal skin(Symptoms include itchy, sore and inflamed vulval skin which cracks, causing additional pain and stinging and treated with a strong steroid cream).All of them except lichen planus can be transmitted after oral or vaginal unprotected sex.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Also you should be able to pick up something form your local chemist for thrush, however I still suggest you see your doctor to get a proper diagnosis.
Cheers
What does the rash look like? Is it just red and itchy? Do you have any discharge? Does the discharge have a dough or yeast kind of smell?
It could just be thrush, but I would go see your doctor for any medication and get Him/Her to look and make sure it is just thrush and not anything else.
For relief of thrush, bath the vaginal area with Bicarb soda with warm water (to balance PH levels) or even white vinegar with warm water to kill any external bacteria. The vinegar will sting but it will relieve the itchy feeling. Use warm hot packs to ease the pain/itchiness. Only wear cotton underwear and loose clothing. Tight pants will irritate it even more. Stay away from foods with starch and yeast, and acidic foods/drinks.
Also, don't use anything with chemicals, fragrance, or soap in it. You can use anti-bacterial soap though.
Hope that helps to relieve the pain a little, and I hope you are well soon. Take care!