Hello,
According to your expected due date (3rd Feb), you ovulated around 19-20th January. You did unprotected sex on fertile days or unsafe period (18th Jan). So there is quite chance of being pregnant in spite of late taking morning after pill (always to be taken within 72 hrs for highest efficacy).
First of all, you need to do a blood test for beta hcg & USG lower abdomen to exclude intrauterine pregnancy. Brownish yellow discharge with late period may indicate
implantation bleeding.
In exclusion of pregnancy, other reasons for delayed period are
ovarian cyst, hormonal imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits etc.
Vaginal infection is also to be ruled out.
Do some investigations to rule out underlying pathology like thyroid profile & other hormone assay, blood sugar & prolactin level etc. One vaginal swab test & urine examination are required. So consult with your doctor and take suggestive measures.
Avoid stress/ tension, take healthy diet with
iron supplements, control body wt and maintain genital hygiene properly. Sore nipple is due to effect of
progesterone. Wear tight breast support.
Take care yourself.