Mama, 4 days delay is still within normal range kasi ang cycle natin ay hindi palaging exact, stress, sleep, diet, lahat yan pwedeng mag-affect, lalo na kung late ka lang nag-period last month tapos mas maaga ngayong cycle start. But if you're worried or if it goes beyond a week, mas safe talaga mag-take ng pregnancy test or check with your OB para sa peace of mind, especially kung may possibility na pregnant ka, better to know agad!