You're thinking in the right direction. It could be irritation from condom use or a yeast infection. Also,my sister's and I also have a similar reaction to super absorbancy peri-pads(can only use kotex brand). It is always best to get a dr to check it to be sure.
It most certainly sounds like you have an STD. Not to worry too much, but it sounds like HPV, (Human pappiloma virus-it's very common and some people don't have sypmtoms.) If that is what you have, you cannever get rid of it, but it is managable. However, can be any other STD also. You need to see your gyno. Even though you wore a condom, it could have broke.