I don't know what to do..

I'm a 21 year old female. Two days ago my boyfriend of 4 months and I had protected sexual intercourse. Last night, I went to go pee and when I looked down after standing I saw something down there. I grabbed on and pulled only to find that a condom had been left. I'm 5 days within my next period so I'm not worried about pregnancy, but I'm definitely worried. Before we got together, we went to get tested for STDs and STIs. He has one that can't be cured. I don't think he came in that particular condom, because we always change them throughout our sessions. But we were sure that when he finished in the last one it was still on him. I'm just kind of freaking out and don't know what to do 😖