How to bring up STD’s?

I think I may have chlamydia. I got tested and am waiting on results, but how do I bring this up with my partner? I’m pretty sure I got it from him, and I’m not mad or anything I know it’s asymptomatic for most and he could have gotten it in the past a long time ago and just didn’t know about it. But how do I bring it up to him without offending him or making it sound like I’m putting blame or shame on it?