URG! I want over my ex

My ex and I went out for 4.5 years. I went through a major anxiety episode and I broke up wiht him in order to sort things out for myself, and because I was having doubts. I had never dated anyone else, as we dated from the age of 16 to almost 21. He was my best friend, my confidant and I could tell him anything. He loved me and allowed me to explore the world both with and without him. I loved him, and we dated long distance while I was away at university. My parents hated him, but the relationship he and I had was a very loving, understanding and healthy relationship. After we broke up he was devastated, and I was still very depressed and anxious. For 8 months after he tried to get me back, and was there for me during the death of my grandmother and great grandmother who both died before christmas. Around Christmas time we slept together, and for about 3 months we saw eachother but were not committed as per my request. I felt I was unable to commit to anyone at that point in time, despite knowing that I loved him and telling him I loved him (which he also told me). I told him I didnt want to become serious again as I was not ready to be serious with life, and so in the end of february he left me saying we should take time to ourselves, and he just wanted to be friends and party also (meaning no sex). I was hurt, but understood and so that day we left on good terms. A month later I went on a date with another guy, and told my ex about it. He didn’t seem bothered by the first date, but was much more unimpressed when I pursued a second date. I accidentally sent my ex a text that was meant for the guy I was sort of seeing, and he was very angry with me. It was after this that he and I both found other partners. A few weeks later he moved in with his new girlfriend, and my new relationship has left me unsatisfied emotionally and missing my best friend. I know he is over me, as when I send him nice emails he doesnt reply, and I had to delete contact with him and his family because it became very painful for me. Now I am with my current boyfriend who is soon to become an ex, and I am not sure how to live single and accept the reality that both my current relationship wasnt meant to be, while still dealing with the reality that my ex boyfriend is happy and will never return to me. Its been almost a year since I have seen him, and a year and a half since we oficially broke up. Please help.