If you are on breast feeding, then it can cause irregular period. Other reasons are hormonal imbalance, stress/anxiety, ovarian cyst
, thyroid problem, wt gain/ extreme loss, irregular eating habits etc.
Need to investigate properly to rule out underlying pathology by USG lower abdomen & complete hormone assay etc.So consult with your doctor and take suggestive measures.
Avoid stress/ tension, take healthy diet with Vitamin & iron supplements
, control body wt and take sound sleep. You may need to take progesterone
pill to regularize period with other supportive medication