There are several reasons for irregular period like ovarian cyst
(most common in your case), hormonal
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, thyroid profile, blood sugar & prolactin
level, blood testosterone level
etc. Consult with your gynecologist for proper guidance 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 hormonal therapy to regularize period with other supportive medication