Should I Be Concerned?

Guys I'm nervous and I really need advice. I had sex for the first time a few days ago with no protection (he pulled out but ugh). The next day (a little more than 24 hours later) I took a plan B but I'm still so nervous. I was supposed to start my period yesterday but I still haven't yet I'm PMSing really bad. I looked into it and apparently the pill can delay your period by a week? How likely/common is this? I'm only 17 and I live with my aunt not my mom and I'm scared if I tell her she'll never trust me again and the friends I had went to about it are all older (19/22). What should I do? I absolutely cannot have a kid or be pregnant and I have no idea on how to handle this, and I still haven't made the guy of the situation aware of any of this.