Im a smoker, & a birth control user.

--I am 19, I have been on Bc's before but just thought id start again, Before i started my birth control i had used 5 plan b contraceptives one pill, one day, each week. for ONLY 5 weeks. (3rd week of November until beginning of December) Bad Mistake, i know. After the last plan b pill, i got my period. So i decided that i start birth control, i didn't start it on the days i got my period because it already passed but i started it 4th week of December (19), Didn't have sex until the 28, then got my period day 10th, month of January. After those 4 days of my period i then didn't have sex until 12th month of February. But THAT day when i had sex, i was on the inactive pills, but i didn't get my period. I don't understand why I had my period Jan, but not February.. the day i had sex in Feb, i was SUPPOSE to be on my period already. Ive taken 4 HPT & all are negative, I am very accurate with the time of my birth controls, & now i am on my LAST pill from my 3rd packet, so this week is when i should get my period, but is it possible to be pregnant?
I have checked everything, calculated the days i had intercourse, the times of my birth control.. but i am not sure.
Just scared, please answer. thanks.
It has now been 55 days since my last cycle, still on birth control