Took Plan B 30 minutes after, 6 days before my period was supposed to start. It's been 6 days after my period was supposed to start and it hasn't?

Pregnancy test. It is likely that Plan B upset your menstrual rhythm. However to be on the safe side you should do a home pregnancy test. If the result is negative, repeat the test in a week, unless you get a period by then. Use first morning urine and follow the instructions for the test carefully. If you do not wish to be pregnant, use contraception all the time, every time. You may consider implanted contraceptive, or IUD. Practice safe sex. Get HPV vaccine.