Does eating simple food like (corn flakes and bread with some cheese)at 3-4am in morning then sleep over it abad thing if its what's side effect?

No. No problem if you are hungry.I see you are pregnant.Best wishes for you and the baby.Salaams.
Not a bad thing. If you are hungry before bed a snack may help you sleep better. Foods that contain tryptophan like cheese, nuts or whole grains may actually improve your sleep. Thank you for trusting Health Tap!