How many days after O can you have Implantation?

I was wondering if any one has heard anything about having implantation around 14 dpo? I'm beginning to think I may have had implantation cramps and bleeding when I was supposed to start my period. I had severe cramps on day one with very light pink spotting. The cramps were so bad I was nauseated and tearing up. I haven't had cramps like that in probably 10 years. On day two I had heavier bleeding which made me think okay it's just my normal period but then on day three I have only had brown discharge! I'm just a little confused!! Any ideas what could be going on?