TMI!! sTD?

Okay so first thing I know, go to the doctor. I am. When they open in an hour. But okay anyways; last week I noticed it hurt when I went pee (thought it was the start of a UTI so I started drinking more water and stuff, problem went away working like 2-3 days. Then my long term SO and I had sex on Sunday and come Monday morning I woke up with this little sore on me. Then today I woke up and there were clear blisters around the initial sore. I’ve been tested but it was more than a year ago and I’ve never had any problems like this before. I don’t plan to bring it up to him until I get results at the doctor but I forsure don’t think he’s cheating on me. Could one of us had something and it just now arise?