Need some Advice..

I broke up with my boyfriend of 8 months weeks ago because I felt like he didn't feel the same way I felt about him. My whole family liked him and his family including his parents loves me and they still do. Turns out after we broke up, he cheated on me with a family friend while we were together. I found out through a friend of his and when I asked him he admitted it. The girl whom he cheated on me with told me that it was just a one time thing, they're just friends, and that she's sorry. I was not only upset, but furious that they did such a thing and I didn't do anything wrong. This guy was my first love, first everything. I saw him in my future and everything.. I loved him. Now that me and him no longer talk, I continuesly see him and her together and it hurts so baldy to see even though I convince myself that I'm over him and he's dead to me...