I am a 23 years old Muslim boy. I have chosen a girl, almost same age as mine form the same University I graduating. I have talked with her several times, passed some times walking in street. I finally choose her to be my life partner. Then I talked to my family about her and both of our family are agreed to our marriage. But its not happening now because I am graduating in 7 months and after the graduation I can marry her. But the family arranged an engagement, we are engaged now. She now believes that I am her husband and I also believe that she is my wife.
What I am asking is, what should we do now? Should we be act as real husband and wife?
Or should we be like separate boy and girl where if I go physical it will become 'jinah'?
What is the marriage according to islam?