Name this movie plz i really need to find it?

do anyone know the name of the movie with the guy had a baboons heart and the girl he saved from getting d or something feel in love with him. he was always quiet. he told the girl he didn't want to get a heart transplant because that was his heart. at the end he wrote her a letter and he told her to read it later but later he died. i hope this is some good info i really wanna find this movie