confession

My fiancé (age25) and I (age24) have been with each other for the past five years. He cheated on me with his friends sister (age21) for a couple of months, nothing emotional relationshipy like was happening between them just physical sex.. I found out and left for a month to clear my head, we talked and Skype the whole time I was away staying at my friends out of state.  We were living together at the time for a year. Now I'm back to living with my parents and we are working things out.. I have learned to look past his infidelity and we are doing better than ever.  But a week ago I got drunk at a coworkers place and everyone had left while I kept drinking with my coworker (age 32) who's place I was at.  We ended up having sex and I didn't get home until 8am cause i fell asleep there.  My fiancé knows what's happened cause I told him the truth that same day during my lunch break at work. He was angry and pushed me away for a week and a half. Now we are trying to work things out again because we both do love each other and see a future with each other.. The thing is No one knows at my job about me and the coworker, and we still go out drinking together but he wants to have a physical sexual relationship with me and stay friends and wants me to stay with my man.