I agree entirely with yeswecan. Either a forgotten tampon or BV, both can make a vagina smell like dead meat.
i dont mean to sound patronising, its just that something similar happened to me a while ago and it turned out that i had forgotten that i had a tampon in. Might be worth checking if you use them as its easily done . If not, get yourself to the GU clinic it could also be bacterial vaginosis (Ive had this too from using over perfumed shower gel on my lady parts!). And not all infections are a result of unprotected sex x