Hey Jennifer,
Perhaps your vagina needs more time to heal as the tissue is probably still tender from the infection. Maybe try waiting a few more days, try having sex again, and see how that feels. If it's no better, I'd definitely go back to the doctor. A yeast infection needs about 10 days to heal so having sex right after the end of the 10th day can still be painful. Let your vagina rest and recover for a few more days (haha that sounds funny) and see if that helps. If not, go back to your doctor. Hope you feel better!