Is The Brown Discharge I Experienced After Taking Duphaston My Period?

Hello doctor, my lmp was 16 of November 2022. My period was supposed to come on December 23. But it was late. I had protected sex on 14 December. Therefore i did a UPT on 4th of January, a blood test on 5th (1.8 hcg) and a tvs on 7th(free fluid in pouch of douglas. And corpus luteum in right ovary). All of this indicates im not pregnant. But technically speaking if conception had to occur it would have been done after 14 December which would make all these tests irrelevant. I went to the doctor. She prescribed dufaston to me. I did a blood test day before yesterday too. My HCG decreased to 1.6 today was my fourth pill of dufaston and I got brown discharge today. Is it my period or am I pregnant?