Plan B problems

So I got off my period December 23rd and had unprotected sex Christmas eve and let him cum in me all day and at the end of the day I used a Plan B. The 27th I was feeling nauseous in the morning and went home from work sick and then later in the day I felt fine. Today’s the 29th and I’m bleeding lightly down there. So is it a new period cause of the Plan B or do I needa see a doctor ASAP please help.