Weird CM/blood

My period ended on June 5th and my fiance and I had sex on June 11th. Today I felt something down there, and I was thinking iy was just regular CM. So I went to the bathroom to wipe it off and I saw CM with what looks like old blood mixed in on my liner. ( I wear a thin liner usually because sometimes my body decides to produce a lot of CM.) It looked kind of like ehat happens when I'm getting off my period. Why would this be happening so long after my period? Or I guess I should call it my withdrawal bleed. I don't get a real period because ive been on the pill for years so they are withdrawal bleeds when I'm on the last week of pills in the pack. Has anyone had this weird cm/blood mixture so long after their withdrawal bleed?