STI- Help!

Hello, so my boyfriend sits me down after I returned to school from spring break and let me know he was diagnosed with Chlamydia and that I possibly might have given it to him. I immediately felt disgusting and horrible but I don’t think that was his intent. He kept telling me he loved me and that its nothing to freak out about and that someone I had sex with before we got together must have had it. So, I now have an appointment scheduled later this week to see if I have it and to get medication. Anyone else ever have this and can tell me what to expect at the appointment? I am 18 and have yet to go to a gynecologist but I am going to my college’s health center’s women’s clinic for it. I am nervous.