Questions about sex,discharge, and implant

So ladies I had the nexplanon in for a couple months and got it out last Thursday the 29th.. Me and my husband had sex the 30th of September and then the 2nd of October. I just recently had my period in the beginning of September and ended late September, my question is i have been having no signs of pregnancy symptoms and I have been having brown discharge the last 2 days, what does that mean? I just took a 5 day sooner pregnancy test and nothing it was negative, not sure if I tested to early and or if I am going to be starting my period if that is what the discharge means... Could anyone help me understand what exactly is going on please!