Here, you need to undergo one blood test
for beta-HCG at the earliest to rule out pregnancy. Early home pregnancy test may give negative result.
Other reasons for delayed period are hormonal imbalance (most common), stress/ anxiety/ mental upset, ovarian cyst
, irregular diet pattern, wt change, thyroid disorder
Consult with your gynecologist for relevant examination & investigation like USG pelvis, complete hormone assay, prolactin level, thyroid profile etc.
Avoid stress by regular deep breathing, take healthy diet with iron supplements
, keep bowel habit regular, control body wt by regular exercise/yoga and take proper sleep.
Be well & take care.