Morning after pill

Hi. I had unprotected sex the day of ovulation and 36 hours later I took the morning after pill. I have no side effects.

But its 9 days past ovulation and 9 days after I took the morning after pill. And this morning light cramps and pink brown spotting literally size of a 5p. Then by mid day it stopped and I've had nothing since.

Could it be implantation bleeding and the pill didn't work or sitting from the pill but surely after 9 days and tiny bit of pink blood then stopped isn't normal?