Why is my period two weeks early?

Anonymous
I'm 14 and I woke up this morning and went to the bathroom and there was blood like my period was starting but I'm not scheduled to start my period for another two weeks. I took the plan b pill earlier this week and I had sex yesterday (not my first time though). I'm also currently on iron supplements and I'm wondering if any of these could be a reason for it? Please and thank you (:
Updates
+1 y
I'm 15 almost 16 not 14 sorry hit the wrong buttons
Why is my period two weeks early?
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