There are several reasons of irregular delayed period,called OLIGOMENORRHOEA.You get negative test and exclude pregnancy
Your features more likely due to Ovarian Cyst/PCOD and other may be hormonal
imbalance,over wt/extreme loss,stress,emotional upset,eating disorder
,thyroid problem etc.
So do a USG lower abdomen with PPBS,LH/FSH,Thyroid profile,Blood estrogen & Progesterone
to rule out underlying pathology.
Then consult with your gynecologist and take advice accordingly.
Control body wt,avoid stress,take healthy diet with avoidance of fatty food and sleep properly.