Why do I miss my ex so much after 7 months when the relationship was toxic?

3 years and we loved hard and we fought hard. In the end, he was an alcoholic and it became to much for me to handle. Drinking al day long. I never knew which version of him I was going to be dealing with. We became violate towards each other in the end. Verbally abuse was horrible and he was worse, but I wasn’t exactly a victim. All I know is I thought that is being apart would be best and I believe it is, yet 7 months later, I find myself thinking about him everyday, most days 30-40 times a day. I have no contact and don’t look stalk or ask questions to anyone. I have no idea what’s going on in his life and not do I want t know. Yet, my soul hurts and I just wish we could go back to what we had the first 2 years. I miss my best friend and lover. I am dating someone else and he is great, yet sometimes I cry when he isn’t looking because something takes me back and I miss him so much. I did email him around the holidays and didn’t hear back. I don’t think he even cares anymore. I ended it and he felt betrayed. Now I am broken and my soul feels empty. All day everyday. It took me 5 months to even go on a date. I still feel like I am cheating! What is wrong with me?