To any obgyn out there, please help, I have strong bad odor down there. What can i do?

Hello, I am 18 years old. So about 4 months ago I got the nexplanon inserted after taking the bc pill for 3 years. I spotted for the first few weeks and therefore I used "always" panty liners. I then stopped spotting, and stopped using liners, but noticed a very strong old-blood/fishy smell. It is very strong and will appear only 2 hours after i shower. I am a very clean person, but i do not douche because i know its not good. I went to the gyn to ask about the smell. We both thought it was BV but ALL TESTS CAME BACK NEGATIVE. I was clear of any stis or yeast infections, etc. I am sexually active with 1 person but during all this, he was away for 3 months. The smell continued even when i wasnt sexually active so I didnt think it was a ph inbalance. The gyn suggested to stop using vagisil ph balance wash and to take florajen 3 probiotics. She believed the was caused by the panty liners but I had not used them for a month. I did everything she said. Only cleaned the oustide(vulva) with water. But 2 months later the smell persists. I am very frustrated. My boyfriend can smell it even when I am in pants. Please help any obgyns!!