Hi I Am 22 Years Old And I Have Been

Hi i am 22 years old and i have been on birth control since i was 15. This past month i was horrible at taking my pills and at the end of the month I did not take my white pills and accidentally waited a week and started a new pack. I still haven't gotten my period. I am a week late but took 2 pregnancy tests and they were both negative. Is this normal to skip a period like this?