Brown spotting?

So yesterday when I used the bathroom I noticed a brown copperish color on the toilet paper when I wiped. I put a pad on thinking AF was on her way but nothing ever came out onto the pad. The next time I used the bathroom there was nothing when I wiped. Now this morning it's back, but even less than yesterday. Could this be old implantation bleeding? I took a test on Saturday and there was an extremely faint second line. I've never experienced this before.