Iud insertion/finding out I have an STI. HELP!!

Me and my boyfriend have been dating for 6 months and he has had sex with one person before me. I lost my virginity to him. I had gotten my Iud inserted about 9 months ago. When i went to my check up my doctor told me one of tests came back positive for Chlamydia. I don’t know what to do??? Obviously i’m going to get treated for it but i must have gotten it from him right? And how do i go about telling him? what if he thinks i’m the one who gave it to him? or breaks up with me? Any advice would help at this point.

Update:

So I told him and he was actually very apologetic and felt bad that he gave it to me. He is getting checked and treated soon and we are still together nothing has changed :)