He is hiding something big under those small lies
Why Does My Boyfriend Continue To Lie To Me About Stupid Little Things - Ie Where He Goes With Friends Or What He Has For Lunch - When He Knows I Always Find Out The Truth And It Just Causes The Argument He Wants To Avoid?
Assure him that you don't have any problems in knowing the truth and help him to change, intead of going for arguements go for discussions as this might lead to something big in future...... Make him understand you more clearly and help him do the same for you.....