Missed Period...Am I pregnant

Hi. So my period was supposed to start last week, all week I’ve been having cramps like I usually do before my period but it never came. I’m a week past my period date and I’m 98% sure that I’m not pregnant because my bf has had a vasectomy and we’ve had sex plenty of times without a condom where he cums in me. I still have that scary thought in the back of my mind though that I could be but it’d be almost impossible right? Am I overreacting?