I'm going to sleep with a co-worker who has a boyfriend
Why would you sleep with your co-worker then?
He said he wanted to go out with me even though he has a boyfriend.
You shouldn't be sleeping with anyone who has a bf. You should only sleep with people who are single.
He said he wanted to be friends with benefits so I'm going to do it.
I still think you should reconsider, sleeping with him is just going to bring you nothing but trouble.