In eyes of God and in people's eyes, living together without marriage is wrong. Even your parents will not agree. Your both attitude can test even you are not in one room or one house. Even you are in one house with your fiancee you cannot see the real him, you will find the real him if the paper is signed and legal. He have no any assurance that you will marry him after you see his attitude. ofcourse he will show you all the good things because he have no assurance that you will stay for him for a lifetime even on his bad side.

 Marry first before living together. Do what is right, and walk in God's eyes way.