Uterine Lining After Plan B?

I had to take Plan B a week ago today. Started my period today after being 4 days late. I have had this happen a few times before I got pregnant with my daughter. Now after 8 months postpartum my periods are much better and less painful.

After the Plan B, my first day of my period (today) resulted in a lot of cramping and a heavier than normal period, but not terrible. I know Plan B causes those symptoms. This came out tonight when I went to the restroom. Is this normal?? I never thought twice about it when I was younger but with me having some health things going on, I want to make sure this isn’t alarming.

Thank you