2 week long period

Jerri • 20. Cali☀️
I am 20 years old and have had my period since I was 11 so I'm pretty sure I know my period (or so I think) I had never missed a period until August of this year, I didn't get my period in September either, now here I am after starting my period and it has been 2 weeks of bleeding. Why could this be? Help!