First of all, you need to undergo one blood test
for beta HCG along with USG lower abdomen at the earliest to confirm intrauterine pregnancy
. Light brown discharge with late period may indicate early sign of miscarriage
. Early pregnancy test may give false negative result.
In exclusion of pregnancy, other reasons for late period with spotting in this context are hormonal
imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits, psychological factor etc.
Then, you may require some investigations to rule out underlying pathology through USG scan, thyroid profile & other hormone assay, blood sugar etc. Consult with your gynecologist and take suggestive measures.
Avoid stress / anxiety, take healthy diet with vitamin & iron supplements
, eat more fruits & vegetables , drink plenty water or juice and maintain genital hygiene properly. For breast discomfort, you can wear tight support.
If you need further consultation with me, then you can visit http://www.healthcaremagic.com/doctors/dr-soumen-patra/63326.
Take care yourself.