Implantation or problem.

Had sex October 30th. Started period on the 1st or 2nd of November, had a lighter period... It ended on Sunday 8th and the last 2 days (13th and 14th) I've had brownish discharge like I would at the end of my period. Took test and it was negative. The discharge is only showing up in the morning and maybe a little at night. I will likely call doctor on Monday. But wondering if I'm crazy for thinking I may be pregnant.