*Usually* a foul odor after having sex is related to a bacterial overgrowth in the vagina. Most women who've experienced this will describe it as fishy. You can get a testing kit from Rite Aid that will let you know if your pH is off. If it it and you're still having the odor, the doctor should be able to prescribe you something to take care of it. Google BV or Bacterial Vaginosis and see if your symptoms match. Also, it could just be the odor his semen made when mixed with your own vaginal fluids. BV usually doesn't just go away all of a sudden, so you should be able to tell the difference. Of course if there's any question of STD's, I'd think of that if it turns out not to be BV.
THERE WERE ALSO SLIGHT ITCHING