Your last period date was 12 January. Perhaps it must have started on 8 or 9 January.
So your fertile zone was 17 to 25 January. You had sexual intercourse on 15, 16 and 17 January. So 17 January was a dicey day for pregnancy.
Your expected date of the next period should be 8 or 9 February (I don't know why you expect your next period on 4 or 6 February).
I suggest you should wait till 12 February, get your
beta HCG level done if you don't get your periods by that day and consult with a Gynaecologist for further management.