Missed Period

What could be the reason for my period being this late besides pregnancy? Latest I’ve ever been was 3 days, but this is basically my whole cycle. It comes every month. I’m not stressed or anything. I have symptoms, some of which I don’t normally have. Cramping in my uterus that feels like it’s coming but it randomly stops. Last night, I randomly got a sore throat and still woke up with it. Can getting sick be a contribution?

SN: I had unprotected sex on the 27th but wouldn’t it be too early to be ‘considered’ pregnant? Also, wouldn’t I have been passed the O day to conceive during my fertile days? I took a PT test yesterday and it was negative.