Emergency contraceptives

Ok so I follow my menstrual cycle pretty well and my period hasn't changed much in some time now. Every once in a while it will come sooner or later then usual and then sticks with whatever that time is for a while and eventually changes again. Lately its been coming on the 30th or 31st of the month and overlaps into the next month. But this month it changed and my period symptoms changed. I normally get cramps for 4 to 5 days before it starts and horrible cramps during the first couple days. My period randomly came yesterday the 21st with no cramps leading up to it or any cramps now that its started. I had a oopsy earlier this month I wanna say between the 13th and 15th. I took emergency contraceptive. Could the plan b have caused my period to do this? Could this be implantation bleeding?