You have gone through all the trouble of convincing your parents for thi marriage. Why? Because you want to be happy with someone. Are you happy? If you arent happy why be with him? Explain to your parents that this is the problem and you cant go on and get married to someone who makes the same mistakes over and over again. You dont want to be with someone you fight with all the time. They only want to see you happy. Convince your fiance that you want to end this. It will be hard on both of you. But its alright. In the long run you will both be happy. And who knows? after the break you may feel the need to get back together and realise each other’s importance and stop fighting.
But first, tell your fiance. Tell him you want to end this. Take your time and space. Pull yourself together. Give it a month. After one month you decide if you want to go back to him or stay this way. Tell your parents later. You can handle this one step at a time.