Hi, I just started nursing school in August and have been very stressed. I am taking Mibelas Fe 12 birth control and the last 4 pills are the sugar pills. Lately I've been feeling nauseas and anxious and not sure if it's due to school or the possibility of being pregnant. I switched to this birth control two months ago and last month when I got my period it started on that Sunday. I have taken 3 pregnancy tests and all have came back negative. How likely is it that I could be pregnant?