Missing period wtf

I was suppose to start my pd yesterday but I’m a day late. I’m freaking myself out now. Short story had sex in July used protection took a plan b and got a period. I’ve had three since plus a visit to my gyno. She didn’t tell me I was pregnant from peeing in a cup or pelvic exam. My hormones are prob out of whack from the pill but I’m freaking out cuz I’m not on bc and I’m missing a period !!! Help