Implantation period? Not sure! Help

My fiancé and I have been having sex, but with a condom. Usually I wouldn't worry because we have protected sex but it's not always 100% garuntee. So last week I started my period or at least I thought I did. I only thought because when I went to the bathroom & wiped it was a brownish red color so I figured I better wear pads. That entire week I had not one dot of blood on any of the pads but only got a reddish brown discharge when I wiped. Does anybody know why this is happening or has experienced this before. This is the first time it's happened to me & usually when I start my period it's a normal flow.