According to your expected due date, you ovulated around 17th January and did unprotected sex on 18th & 19th which were unsafe or fertile period. So there is high chance of being pregnant.
Do a urine/blood test
to confirm/exclude pregnancy
if you missed period more than 1 wk. On the other hand, if you get negative test, then need to do USG lower abdomen and some hormone tests to rule out underlying pathology if any. Consult with your doctor regarding this.
by yoga/deep breathing, Control body wt, Take healthy diet, take Cap PRIMOSA
daily and wear tight breast support for some relief, maintain personal hygiene and need proper sleep.
Practice safe sex in future. Be well.