You most likely have one of a few different conditions or perhaps more than one and I would suggest that you schedule an appointment with your OB/GYN. I certainly agree that a urinary tract infection
is one possibility. Burning with urination especially a couple days after having intercourse is definitely a symptom consistent with a urinary tract infection. However, urinary tract infections do not cause vaginal discharge. This can only be explained by a vaginal infection
or potentially infection of the cervix. Since you had unprotected sex, your doctor
will and want to entertain the possibility that you have an STD. An infection with chlamydia or gonorrhea could cause these symptoms. The other possibility that you mentioned is a yeast infection. Yeast infections typically are not caused by protected sexual intercourse. However, they do cause a whitish discharge and can result in significant vaginal irritation. I would suggest that you schedule an appointment with your OB/GYN. You need a urinalysis to rule out urinary tract infection and a comprehensive pelvic exam to take a look at these lesions in your vagina and the discharge you're having. Your doctor may choose to perform and in office test for chlamydia and gonorrhea and might also look at the discharge to see if there are signs of the yeast infection or bacterial infection of the vagina.