Genital Sores. Worried as it gets worse.

20 yr old female, 5'5" 110lbs. I had sex almost two weeks ago. A condom was used but not the whole time. Less than one week ago, I noticed burning while peeing and i've had white discharge. I assumed it was a UTI and for three days have been taking bactrim that i was prescribed by a doctor here in MX while i'm on vacation. It has done nothing so far and i'm thinking this is more than a UTI. I noticed a sore on my butt nine days after having sex. the day after, a smaller sore on my vagina. The one on my butt has gotten bigger, redder, and little bumps have formed around the sore. I obviously have some sort of STD but don't know which one. I'm out of the country for a few more days and am waiting to see my doctor until i'm back but in the meantime am very worried as it gets worse.