The Unfaithful Friend My closest confidant slept with my husband/wife /girlfr—should I confront her?

I was with my boyfriend for close to four years. We lived together and planned on marrying. A month ago I went on a trip for a week, when I returned my bf and I talked and decided that we both needed some time to make sure we still wanted the same things. He never moved out and we never really stopped dating. Last week we decided that we couldn't live without each other and we were going to work it out. After reaching this decision I recieved a text from a friend letting me know that while I was on my trip my bf slept with my best friend. (Mind you we were still together at this point)He addmitted to the afair. I kicked him out of the house and I will never speak to my friend again. I am so hurt by all of this. Has anyone experienced this? Any advice for easing the pain. I loved him I wanted to marry him. How could they do this to me? I am so hurt.