Taking the morning after pill

Hi ladies. I had unprotected sex on Sunday 8th and I took a morning after pill (Postinor 2) the next day, Monday 9th. Leading up to today (Sunday 15th) I felt pms symptoms and I started bleeding. Is this normal? I know my period can come earlier or can be a bit delayed but it's only been 1 week since I took the pill and my period Is back already. Should I worry?