alien movie

hey guys i need to kno the name of a movie bout an alien.......i saw half the movie some years ago..........it was bout an alien which comes to a small town or something.....it can possess any human body......at first it possesses a lady and later possesses the body of the lead actress's boyfriend......the movie starts with showing this girl's life and all.........

i really wanna know the name of the movie.....hope someone can help.......

thanx😊