It seems to be allergic dermatitis
have you started some medication which is new? and for what is that medication?
Another thing is are you having your menstrual cycle normal?
Any complaints on passing urine?
have you had unprotected sex preceding this problem?
How to manage?
1. Use cotton undergarments and do not keep your dressed for long hours in a single dress.
2. Maintain genital hygeine.
3. use coconut oil to apply on the rashes.
4. No sex till you recover from this problem.
5. drink lots of water and you can have a couple of crushed cloves of garlic with a cup of lukewarm water daily. if you find it affecting you adversely then discontinue.
6. avoid spicy and junk food.
7. have faith in your doctor, it might take sometime.
You can also consult Homoeopathy, it is also quiet effective.
Wish you a speedy recovery to health.