TMI no pic. Approx 12 DPO

After using the bathroom, #2, I wiped and got a lot of mucus that was light pink/ brown. When I used the bathroom earlier I had hardly any mucus at all. Is it possible that it could be implantation bleeding. Normally when I spot before AF shows it is brown. AF isn't supposed to show until Monday or Tuesday for a 25 to 26 day cycle. Should it be a concern if my cycles keep getting shorter?