I need a big sister

So to give context I’m 17 and I don’t know what the hell is going on. I had sex the Sunday after 4/20 and it was, without a condom. He DIDNT explode but it was unprotected and the concern was could it affect me. The following day (4/21) I did get plan b and was supposed to start my period 4/22. I spotted Tuesday but it didnt continue today and I’m wondering if the plan b could have affected it or if it’s because of something else 😭 yk???

Anyway I need help.