First of all, do a blood test
for beta HCG or USG pelvis to confirm intrauterine pregnancy
. Early pregnancy test may give false negative result.
In exclusion of pregnancy, other reasons are hormonal
imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits etc.
Do some investigations to rule out underlying pathology like thyroid profile & other hormone assay etc. Regarding this, you consult with your doctor to take suggestive measures.
Avoid stress, take healthy diet with iron supplements
, control body wt and need adequate sleeping.
If you need further consultation with me, then you can visit http://www.healthcaremagic.com/doctors/dr-soumen-patra/63326.
Take care yourself.