I Had Unprotected Sex With A Girl On The First

I had unprotected sex with a girl on the first date. 2weeks after I realize I messed up and got a std check and I was clean. So I naturally continued to see her. We have continued to have unprotected sex for the past 4 months. Two weeks ago even after she told me she a mild yeast infection from taking antibiotics due to her having strep we had an amazing two day escapade, but after the first day I realized that It was as if I had glass in my urethra. This was Monday and Tuesday. I thought I may have just rubbed my self raw, but Friday I went for a std check and this following Friday today found out I had chlamydia. Is it probably a good chance she has been sleeping with some one else?
I got the medicine and plan to inform her tomorrow. I also have information to give to her.