Thanks for your question.
Delayed period is a sign of many physiological & pathological problems.
Physiological possibilities include pregnancy
, breast feeding etc.
Pathological causes could be any medicine, stress, hormonal
or genital tract problems.
I think you should go for a blood pregnancy test & a fresh trans-vaginal ultrasound
as some times a very early or ectopic pregnancy may be missed by conventional home pregnancy tests.
Hope I have given you the desired clues.
Best of luck.