please help

ok so prob going to get judged awfully for this so before someone tells me how I shouldn't have done this, I know. recently my boyfriend and I had sex for the first time, we are both 16, and we did not use a condom. he pulled out but cummed like around my waist and it dropped down to my vag so it didn't necessarily go inside I don't think but it definitely touched it. I told my mom and she took me to get the morning after pill and I took it probably 3 hours after this happened. my period was supposed to come today and he been having cramps but no spotting or blood. (plan b can cause periods to be late tho) but point is I don't think it's easy to get pregnant a few days before your designated period? what are the chances I could actually be pregnant after taking the pill and under other circumstances? my mom thinks I'm crazy for being so worried, but it's more of my boyfriend who is so scared and I just want some insight.