You might have an sti or other infection.Get tested dont let shame or fear ruin your health its not worth it. It could also just be a hormonal imbalance.
are you alergic to tampons or sanis is it itchy discharge ?or smelly then it could be a urine infection or thrush most people get slight thrush after their periods try changing your brand of sanis /tampons or have you changed your soap powder lately that could affect you hope ive helped
It might be time for you to find another doctor if you are not getting answers that are helping you. There are many testing kits sold right by pharmacy counters that can test for different infections. Could it be a reaction to a birth control you are using?