How to know if plan b changed your uterine lining?

If plan b changed your uterine lining (thinning it out so the fertilized egg does attach to the uterus) while you have spotting for a few days?

I took a plan b during my cycle. I had sex my boyfriend and he came into me (we didn’t realize the condom tore until afterwards). My cycle stopped the next day.. 5 days after that I I have been spotting and today makes the 3 days of that.