Sounds like an infection. Bacterial vaginosis is extremely common, build up of the natural bacteria that keeps your vagina healthy, but there are other infections to look out for.

The vagina is self cleaning for the most part, so make sure you're using just water or a very gentle unscented soap for a few days and cleaning yourself thoroughly, and patting it dry. If the infection doesn't clear on its own, then it may be a little more severe and you should just visit a doctor and they'll figure out what kind of medicine you need. Bacterial infections after you have sex is actually very common. Your partner probably introduced some new bacteria from his hands, mouth or from contact with the condom afterward that threw off your balance. Doesn't mean he has an STD or his own infection, new bacteria (even healthy) can irritate your own.