Implantation bleeding or just leftover blood

TMI for everything in post: last period on 11/26,had intercourse last Sunday didn’t use protection.Now by app I should be in my fertile days this week (I know it is not 100% sure) but now my dishcharge is off white stretchy and with blood thru it (picture attached).Could this be implatation bleeding?

(We already have kids but this never showed before)