Dear , u must be aware of normal menstrual cycle , getting delay lots of reason , most immediate reason if have sexual activity , so u first rule out from your side , then consult doctor for definatve treatment.
Second thing , emotional stress , lots of exertion ,junk food , lots of alcohol can distrust menstrual cycle so try to avoid it
Next Steps
consult doctor ,u can consult me too
Health Tips
healthy diet , yoga pranayama , avoid alcohols and outside food