I think I have an STD...can someone please help me confirm?

I performed on this guy on New Years Eve, and then I got sick after wards with a sore throat. I've been sick for a week with a cold/coughing now but I'm getting better...my sore throat has pretty much gone away but now it feels like there's a canker sore on my throat...could it be an STD? I wanted to get somebody's opinion before I went to a doctor to be tested.