After sex, I smelled a strong and bad odor from my vagina. Why?

Hi doctor,

I am 47 years old and I do not have any vaginal or reproductive issues. I do not have any odd odors. I am vegan and I had a pleasant smell in my vagina before the incident. Today, I had sex with my boyfriend. After a minute, I smelled a strong and bad odor. It does not seem to be fishy or yeasty. But it was a bad odor. He has not taken shower this morning and he was wearing new undies that looked to be synthetic and unbreathable. I noticed a strong odor coming off from him. I was mortified and blamed myself and we stopped immediately. After returning back to home, I tried to assess my situation once again. I searched online and could not find anything regarding the symptoms of smell. Then I started to have a bad smell in my vagina after having sex. Is it possible to have this issue after doing deep penetration? because my vagina smells a lot after sex. Does he have fostering the bacteria? Does it become activated when it came in contact with my fluids?