Whats going on with me? Implantation ?

So after 3 years of TTC and 5 months of using glow and ovia I am experiencing something odd. I am on CD 21, AF due in 10 or 11 days, I ovulated on the 19(used LH strips), and my body just within the last 3 hours has been acting funny. All day I had weird cm for this point in my cycle, but the last few hours I have been cramping (lower abdomen only when normally my AF is higher up and down my legs), and having lower back pain on my left side. Is this a sign of implantation ?