You're Using the Wrong Condoms or Lube
Some women are more sensitive than others when it comes to condoms or lube. If you're using something that doesn't sit well with your body or has certain ingredients, you might smell something weird coming from down below after sex. It might be rubbery, musky, metallic, etc.
Experiment with different condoms and lube with your partner until you find the one that works right for you. If you still find that you're experiencing discomfort or strange scents from your vagina, speak to your doctor.