Plan B

My Fiancé and I have been together for a little over fives years. This month we had an accident where a condom broke. It occurred about 4 days after my fertile window according the app. I took plan b the next day. It's been 2 weeks, my period is a week late. I've tested and keep getting negatives. Am I late because of the pill, or am I pregnant? I'm kinda freaking out a little bit. We're in the middle of buying a house and a lot of other changes, so I'm not sure if this is all from stress etc.