My friend's boyfriend used to be my housemate and I slept with him and ended up giving them both chlamydia.
Were you aware you had chlamydia?
Yes, but I did it anyway.
It's terrible enough to sleep with your friend's boyfriend, but deliberately exposing them to an STD is a bit immoral. You should never sleep with a partner in a relationship as well because they might break up now because of you.
You are being judgmental.
Trust me, I don't want to judge you at all, but what you did was pretty bad and you probably know that. That's why you are telling me because I sense there is a part of you that is feeling a bit of guilt. Hindsight is always 20/20, so hopefully going forward you are more aware of your actions.