I had my last period on 4-Oct-11, I used to have regular period cycle of 28 days but since last 2 months it has been delayed by 1 day each month. And this month I am yet to get my periods. I have checked my BBT this month from beginning of the month and it has been high and is in the range of 98.3-98.8. I took a pregnancy test 2 days back but it came negative. Could I be pregnant? I am taking anti-histamines, will these affect the pregnancy test results?