Should I forgive my boyfriend for talking about his and his ex girlfriends life?

Leave him. Hes not done with his fixation of their life. I could see if he just mentioned it for help in a convo but he took it way too far. He said he misses it and if he could go back...sounds to me like he still wants her and if he could, would still be with her. You deserve to be number one and all he thinks about when it comes to intimacy! You will never be able to forgive him or if you think you can it will haunt you! Good luck! I hope you find a better guy!