First of all, you need to undergo one blood test
for beta-hCG to exclude late pregnancy.
Other reasons of long time missed period are ovarian cyst
or PCOD, obesity, stress, pelvic infection
, hormonal imbalance, mental stress/ anxiety, irregular diet habit etc.
Some basic investigation like USG, hormone assay, thyroid profile etc are required after proper examination by your gynecologist. Take suggestive measures accordingly.
Take healthy diet, avoid stress, control body wt and maintain genital hygiene. Wear tight breast support to get some relief. Take some antacid to remove indigestion
problem. Hope it helps.