First thing, you should undergo one blood test
for beta HCG to confirm or exclude pregnancy
status as you were involved in unprotected sex. It may indicate implantation
bleeding. TVS scan may be required around 4-5 weeks to check product of conception.
In exclusion of pregnancy, reasons for irregular spotting are hormonal
imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits, psychological factor etc.
Some investigations are needed to rule out causative factors through USG pelvis, thyroid profile & other hormone assay etc. Consult with your gynecologist and take suggestive measures.
Avoid stress / anxiety, take healthy diet with iron supplements
, eat more fruits & vegetables, control body weight 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.