Sporting- normal?

So I’m 21 years old and have had my period since I was 9. My cycles have always been 28/29 days. Never earlier or later.

I’m on cycle day 16, and yesterday night I noticed I had some spotting as well as this afternoon. Just pink/light red. Enough to stain my underwear but not anything else. I’m not on birth control or any medications. I am sexually active but haven’t had sex since last week. Is this normal? Should I be concerned ? Do I call my doctor ? Sorry if this is a stupid question but itsnever happened before