Possible Sign Of Prego.! BFP Hopefully.!

I'm Supposed To Start My Period On 21st.. Yesterday Used The Bathroom And Wiped And It Was Brown Like Old Blood.. That Was One Time.. Since Then Nothing Else On Tissue.. Me And Hubby Just Had Sex And Nothing Came Out.. Which Is Odd Because Usually If We Have Sex The Day Before Or Day Of My Period I Start Spotting And Nothing Yet.! What Do You Ladies Think.? Do You Usually Have Old Blood ComebOut The Day Before Or Day Of Period.? Input Please.!