Talk to Gynecologist on Missed Periods And Pregnancy Concern

Assalam u Alaikum Doctor, my periods are usually regular and normally come on time. Sometimes they may be 1–2 days early or late, but this has never happened before that my periods are delayed for 12 days. I took a urine pregnancy test at home when my periods were late, and it came back negative. I also had a blood pregnancy test done on the 11th day of missed periods, and that was negative as well. I am worried because this kind of delay has never happened to me before. Could this still be pregnancy, or could there be another reason for my missed periods?