period after plan b

I started my birth control pill pack a day late, and a Monday, I usually start on Sunday. On Tuesday I took plan b just in case. A little over a week later I got my period, and am currently on day 13. Is this normal? I thought it was ending, but then this week is the week I normally get my period, and it sort of picked back up again. I feel like this is normal but I’m not sure?