how do i do this

how do i stop talking to my ex i love him but i just don't want to be with ... he abused me before in the past and i can see he changed he is genuine and caring and was going through a terrible time in life as was i ... together since we were 14 and 16 .. 5 and a half years together and i just left finally in march because i wasn't happy anymore and we lacked a lot of things it just felt toxic and draining .. he's so apologetic and feels terrible for the past i know he truly does. He realized everything he needed to change and what was wrong before and now that he's showing it i just don't feel like i want to get back together ever. Am i wrong for this ? he makes me feel kind of guilty like god always brings us back to eachother so why give up now etc but i SIMPLY do not want it. I met someone else that makes me so happy and does everything i ever wanted in a relationship treats me like a queen and i want him in my life i don't want to mess this up especially for someone who already had their chance and hurt me .. what do i do i just feel crazy sometimes because he wont leave me alone.