I Juat Went Off My Period On Dec 2 And

I juat went off my period on Dec 2 and Dec 3 and Dec 4 had unprotected sex with my bf on Sunday 4th later that evening I went to the bathroom and when I wiped a string like snot with what looked like blood came out when I wiped ... Today is the 6th of Dec and im having like lower cramping. .. What could this be..