Implantation bleeding ?

So I was bleeding about a week ago , very lightly & it was a super light pink & never got on my underwear (only lasted 2 days), my period is now 4 days late & the last time I had unprotected sex (no condom but was still on BC at the time ) was about a little over 2 weeks ago , however I am just getting off the depo shot .. could this be implantation bleeding or just a side effect of coming off the shot?