After 10yrs of being engaged,and loving my partner even when he's been horrible to me,why am i feeling so emotionless now? He started working on the things he messed up,but i don't love him.Why?

First of all, good for the both of you, that he is starting to change and is working on your problems. If he hurt you in your past it is normal to become somewhat detached. It is just a normal mechanism in you to prefent further pain. To move forward, give him a chance to change and correct his mistakes. It will take a while for you to truely notice it. Even if your mind sees the changes allready, your heart will need time. It might help, to talk to him about how you feel. If you want to do that, try to make sure, that you dont accuse him and notice that he is trying to change. Maybe try to have date-nights again. Create some time you just spend purely with your relationship. No talk about appointments, grocery shopping and so on. This could help you to fall in love again. If none is helping and this keeps going on for quit some time, consider a couple therapy. This is always a good way. You have a professional third person who is neutral and who can help to translate and negotiate between you.