I hope your provider tested you since they suspected and std. Or does that make too much sense? The way people do things these days, it probably does. But yes, you would be doing yourself a world of good getting tested to make sure.
It can be from a STD like gonorrhea, chlymida or Trich...doesn meant that it is from one of those. Only way to know it to test for those STD's before you have any treatment. If you test positive bf will have to test also. And if he is positive then someone probably cheated.
I recommend both you and bf test because if it is a STD that is left untreated in him then most likely he will give it back to you.