Implantation?

So, I thought AF came 29th evening. Small (tiny amount) red blood, then nothing but brown and super light for 2 days following. No period cramps( I usually have SEVERE cramps) or any pms symptoms to speak of...just a small amount of back pain. Could this be implantation bleeding? I'm normally a 31 day cycle which means I would have ovulated around the 20th? If I'm calculating that right?