Had unprotected sex an took Plan B same day now my periods 5days late, a week ago I got a negative pregnancy test? . What's going on?

Cycle may be off. Taking Plan B may definateky affect your next cycke's onset. If more than one week to 10 days late, a pregnancy test is advised. Rest assured that taking Plan B the same day of unprotected sex is very wise, and very effective. A recent negative preg test is also reassuring. Give it a few more days. Up to 10 days at max.