Should I be worried... is this normal? Need advice

I’m 13 dpo. I had a positive pregnancy test on 10dpo. My lines have gotten progressively darker. I would normally be getting my period today or tomorrow. Just went to the restroom and noticed brown cm. I have a positive already, so it can’t be from implantation, can it? It makes me nervous. Does anyone have any advice for me or info on this? Thanks much.