Crazy period?

I was supposed to get my period on the 14th. Nothing came but I had slight cramps leading up to the 14th and up until the 17th I think. My calendar says it ends on the 18th.. nothing at all today I went to wipe ( around 12pm) and noticed very dark brown discharge thinking okay its my period .. (around 6pm-currently) now there barely anything on the pad so I'm not sure anyone been through this?? My boobs still are sore and I still feel nauseous... still slight cramps as well but I can't tell the difference in pain since I was just in a car accident 2 night ago:(