I slept with a married man, now I have an STI

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I have been having some pains and went for some tests about two weeks ago. When the results were out, the doctor said that I had Chlamydia which she said was a deadly STI and was at an advanced stage. My only sexual partner for about a year and half is married and has one child. I don't know where this could have come from but I am wondering how to tell him so he could get tested as well as have his wife tested. I was told this can have severe implications which include pelvic infection and infertility. I hope I can save her from such adverse effects. I want to help but I am afraid he will think I am the one who infected him and put his wife at risk. What do I do? I need your advice...{Lilly}