This line is from the song 'Karvate Badalte Rahen' from the 1968 film 'Aamne Saamne'. The line 'Karvate badalte rahen...saari raat hum' means 'We kept turning sides (in bed)...all night'. This describes sleeplessness due to thoughts of the beloved - tossing and turning throughout the night. The other options are incorrect: 'teri yaad mein' (in your memory) changes the meaning slightly, 'tumhe yaad karke' (remembering you) and 'bus tumhe yaad karte rahen' (just kept remembering you) are not the actual lyrics.