Period or Pregnant?

Quick question
I am currently on CD 27 with my period due anywhere from tomorrow till Monday.
Today I have had some very dark brown blood (probably half a teaspoon) mixed in with what I would call creamy CM (sorry if TMI).
I normally have bright red blood on Day 1 of period so this is a little unusual. However I have also have abdminal cramping since CD14.
Is this what you would call implantation bleeding?
Is it normal to have some bleeding when your period os due even though you may be pregnant?
I am testing tomorrow morning.
Thanks ladies - your help is always appreciated.

Um probably too late for implant bleed that would normally happen 7 - 10 days after you o... I would do a test in the morning and hope for the best... Have you been off the pill for long?? Sometimes after coming off the pill your periods change from the norm you had.. Good luck...

Thanks Janeo
I have been off the pill since June.
Bugger - looks like AF is on her way.
I thought this month was the month....