AF or Implantation Bleeding?

Michelle • Mother to a beautiful baby girl, and a proud step mother to a loving little boy! 👨‍👩‍👧‍👦
I am using three apps for period tracking; My Days, Ovia, and Glow. Glow is the only app that indicates i am supposed to have a period starting yesterday. My other two apps say the 19th is af's potential arrival. I pray she decides not to come.
Yesterday i had some cramping and discomfort. Today i have had even more cramping and discomfort. Now its also accompanied with lower back pain. 
Just went to the bathroom and had some brownish discharge. I pray this is not aunt flows early arrival! 😥
I have been moody, tired, breast are tender, and anxious these last few weeks.