Could I be pregnant??

I had unprotected sex on November 4th and he came inside of me. I took a plan b two days after which was November 6. after taking that I didn't get any side effects no symptoms. The app says it was on my fertile day and there was a 27% chance of pregnancy. I was supposed to get my period November 20th and I didn't haven't gotten it and today is November 25. when should I test