Implantation Spotting?

So I'm between 5 and 6 dpo. Today, while at work, I went to the bathroom and had brownish/red on the TP. I immediately got stressed out thinking my period would be starting (but why so early)??? I put a tampon in right away since I don't have time to constantly run to the bathroom (I'm a nurse - don't get a ton of bathroom breaks). About 4 hours later, I took it out and there was just brown on it. At the time of the brownish/red spotting, I had some back cramps but not bad. I'm no longer having any of those symptoms. Could it have been implantation? I've never had that before and I've been pregnant twice but both ended in miscarriage.