My bf is a virgin as well and I am his first girlfriend and sexual partner so, I am sure I havent got a STD.....
Many different infections, chemical/PH imbalances, and STDs can all come off with a bad odor as a symptom. Many STDs are just contracted by any type of sexual contact, not just sexual intercourse. If neither of you have been tested, you may just want to do that anyways to know your standing. If the smell persists, then I would make a doctor's appointment. It's probably an infection and you can clear it up within a week.