I'm sorry to hear this about the mental torture. I too had lost myself in my former relationship. It took our break-up for me to begin to find myself again. It took a lot of effort and time, but I think I came out the other end a better person. I also managed to find internal peace (and it's a great feeling). Unfortunately, it is like a relationship; if you don't continue working at it, it slowly slips away too.
I pray that you will do what is needed in order to repair the damage done and also come out the other end as a better, stronger person. The key for me was to seek understanding. Even though you may not agree with what the other person did, as long as you can understand WHY they did what they did, it opens the door to forgiveness and forgiveness sets YOU free.