At first, I suggest you to undergo one blood test
for beta HCG
along with USG lower abdomen at the earliest to rule out late pregnancy
. Early pregnancy test may give false negative result.
In exclusion of pregnancy, other reasons for late period in this context are hormonal
imbalance, stress/ anxiety, thyroid
problem, wt gain/ extreme loss, irregular eating habits, psychological factor etc.
After that, you may require some investigations to rule out some underlying pathology through USG scan, complete hormone profile, thyroid test, blood sugar etc. Consult with your doctor and take suggestive measures.
Avoid stress / anxiety, take healthy diet with Vitamin & FOLIC supplements, eat more fruits & vegetables, drink plenty water or juice and maintain genital hygiene properly.
If you need further consultation with me, then you can visit http://www.healthcaremagic.com/doctors/dr-soumen-patra/63326.
Take care yourself.