Implantation Question

Could implantation take place later than 12dpo? I was late for my period.. but then ended up what I thought was it starting but it wasn't my normal period.

Normal for me is bleeding heavily through a ultra tampon every 2 hours.....

I wasn't even needing a pad.....

It was red, and then brown the next day. Lasted 3 days. Now nothing

I am now cramping, and lower back pain....

HELP! I have not taken a test since the bleeding started.