Okay i need so advice

A couple weeks ago I was having sex with whom is now my ex. He possibly may not have pulled out completely in time. To make this worse, it was right in the middle of my fertile window and now ive been late for my period by four days. I'm getting a medical test Monday, and if its positive I cannot keep it and absolutely cannot tell my parents. (I'm 17) anything other than pregnancy that could cause this? I've never been late before and a few days ago ibwas having really intense cramps that usually come with my period , but they just stopped. I've been super freaked out for days... any thoughts?