Brown discharge

Hey guys,

So I’m a bit confused and afraid. I had unprotected sex last Sunday and I ended up taking a plan b pill on Monday. I also had sex this weekend. 2 times my partner used a condom and the other 2 times he didn’t. This was Friday & Saturday. Anyhow, this morning I woke up with slight cramping and when I wiped there was brown to bright red discharge. Like you get before your period. However, my period isn’t supposed to come until around the 28th of this month. Which is late next week. Could this just be normal spotting (though it’s never happened like this before) or is there a chance it could be implantation bleeding? If it is implantation bleeding if I take a pregnancy test, will it be accurate? 😭