Can doctors tell if I’ve taken Plan B or not?

Can doctors tell if I’ve taken Plan B?

I took Plan B last week while my boyfriend was in town. To preface this, I come from a very strict religious family and my parents explicitly told me not to have any sexual relations w my boyfriend while he was in town. However, I went against their wishes and did it anyway . I woke up this morning and noticed I was having my period. My mom found out that I was having my period, which was only ten days after my last period, and demanded to know if I had had sex with my boyfriend while he was here. After I denied it, she claimed she would take my to the OBGYN to get me tested for illnesses because an early period is an “abnormality for me.”

I am wondering if it is possible for doctors to tell if I have taken Plan B? I was hoping I could just deny it and that they could say it might be an abnormality of some sort. I really, really cannot risk my parents finding out. Or is there another excuse I can use? Any help?

Can doctors tell if I’ve taken Plan B or not?