If he ejaculated heavily, and you had an orgasm, your sexual fluids are mixed as they drain back out of your vagina. His semen has a distinctive scent, but your vaginal fluid doesn't usually have much smell. It's possible your Skeen's gland over produces this vaginal fluid. That's actually good, so don't worry. If you had a very strong orgasm, this fluid may be more in volume than some women's. If you feel this fluid coming out when you masturbate, you'll notice it has very little scent, other than your own personal vaginal smell. As a man, I notice the difference. You're mainly smelling the mixture.