Thanks for giving proper details .
From your history most most common causes which have caused this pigmentation are hair removal method (waxing > shaving), chemical contacts like veet creams, and also scratching secondary to itching at Vaginal and surrounding areas .
Pigmentation develop due to repeated friction due to scratching. Pigmentation can develop due to repeated waxing , frictional shaving methods. Also some people can develop post inflammatory pigmentation due to irritation caused by creams like Veet.
So I will suggest you for LASER HAIR REMOVAL OF hairs on your private parts.
Pigmentation can be treated well with chemical peels/ lasers / lightening creams and avoiding above culprits.
Next Steps
Don’t get depressed. Consult a certified dermatologist for proper advice and treatment. You will need few treatment like lasers for hair removal and pigment removal in clinic as I mentioned above