I m not absolutely certain when my last period was, but I think it was around Feb 3rd. The time between my periods are not always the same, and in recent months, my period has been coming 1-3 days later. It s now March 11th and I haven t had my period this month yet. I am sexually active, but I always use a condom, and none of the condoms have broken. I took a pregnancy test as well and it came back negative, so what could be the problem?