I am an emotional wreck. Should I cut him out of my life?

[BRi]

I moved away from home about 7 months ago. I ended things with my fiance, almost 4 months ago, due to his unfaithfulness & lies. Since the break up I had been having a very hard time getting over things, facing depression, guilt & I was just very sad all together, some days I didn't even want to get out of bed. Through all of this cousin, whom I love more than anything was by my side throughout everything! Calling me everyday & just making sure that I was OK. Since moving away from town I have cut a lot of people out of my life, friends that were no good & even some family members. People who I felt were bringing me down. About a month ago a very close friend of mines brother wrote me & told me that my friend(his sister) & my ex had been having sex during our whole relationship. Of course I was devastated, but at that point I felt that I had come so far that I didn't want to go back. So I never confronted her or asked her if it was true. I just let it go & kept moving on. My cousin knew how bad that hurt me, & he kept telling me everyday to get over it & move on, & that there were both nothing, so I was. Today while I was on the phone with my cousin he tells me that he confronted my friend on facebook regarding the situation, I was furious!! I am a grown woman, not to mention that if I wanted to confront her I would of, it was my choice not to. I was so hurt! Of course she denied it, but I didn't even care, how could he do that, & it's been more than a month since we first found out about them being together, why would he wait so long to confront her! & why not ask me or come to me first & ask me if I was OK with it. I didn't want her to know that I was hurt, or sad or anything. I just wanted to move on! & now I feel as though I am going back once again, because now this is fresh on my mind once again! When I confronted my cousin as to why he did this, he just said "because I hate her" he hates her for his own reasons, so he should of confronted her regarding there