So I've Been On Birth Control For A Few Months

So I've been on birth control for a few months now and never missed a pill. This past month I missed a couple in a row (mind you, sexually active) around the second week into my pack. I bled irregularly for 2 days. Then once got back on track it stopped. Then about 7 days before my expected period I lost the pack so stopped all together. I am now 6 days late on my regular period. I took a pregnancy test about 4 days ago and was negative. Could I be pregnant? What should I do since I should be back on birth control if I'm not pregnant?