If you are having 28-30 day cycles previously, you may wait for a few days for your period. If you had the spotting on the days corresponding to your cycle, it could also be some hormonal
imbalance. You can repeat the pregnancy
test and ask for the report of the sonogram. Norethisterone
is not advisable if you suspect pregnancy. You can get a blood test
for pregnancy done. Please contact your doctor for further advice. Good luck.