Unprotected sex with friend during your period (19 & 20th January) is very much safe period and chance of pregnancy
is almost nil.
according to your LMP, expected due date was around 4th January and you & your boyfriend involved in sex on 2nd January which was unsafe/fertile period. So there is high chance of being pregnant by your boyfriend.
Do a home pregnancy test or blood test
for beta hcg
to confirm pregnancy as you missed period with light spotting.
After confirmation of pregnancy, you should perform one DNA test for 100% assurance of paternity.