Can implantation bleeding happen at 12 & 13 DPO? Also can it be brown in color?

I’m super confused as to what going on with my body. I got a faint positive at 8 DPO and then at 9 DPO and every day since tests have been negative. At 11 DPO in the evening I had some brownish bleeding. I figured it was my period starting. When I got up this morning there was nothing..no bleeding. Then I had some more brownish bleeding but not much at all. Is this my period starting or implantation?

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