Moving on advice

I just recently got out of what I guess could be considered a relationship. Things were never official but for 8 months I dated, and trusted this guy in every way a person could. I love him still but things started to go down hill about five months in. I found out he had had a girlfriend that he was cheating on with me, a girl he had been with for five years. After I found out I did end up forgiving him and thought things would stop and we could just be friends. Im not an angel and I made mistakes and kept seeing him. I made him tell her and he supposedly did. Months later I tell him he has to make a decision, me or her. He chose her. I understood but wanted to talk to her which I had never even done before. I spoke to her and found out she never even knew about me and he never told her. I told her everything, gave her proof and definitely said some hurtful things to said guy and he then blocked me. I tried to contact him about once or twice after but he completely cut me out and I gave up trying to speak to him but it is still very painful. I have no access to what was my best friend for the past almost year. And I dont have any idea how to move on without closure. I need help please, any advice or excercises or tips to help me? You can ask more questions about the situation if youd like too and I can alaborate to help you understand everything