Week late 😱

So today my period is a week late. We used condoms (one time he stuck in in without one for like 3 sec. And I screamed and told him to get one one but according to my app, I wasn't even around ovulation). My period has NEVER been late unless I was pregnant. I took a pregnancy test at day 5 and it was negative. We just had our baby boy 7 months ago. He's our 4th child and we decided we are done with the baby making. My husband actually has a vasectomy appointment on March 3rd! 
Anyway, I think I'm one of the few people on glow who currently doesn't want to have a baby.  Has this ever happened to anyone?? Could there be another reason my period is late? I made a dr appointment but I'm looking to you guys to make me feel better until then! Haha!