I hope you are pregnant, since your cycle is a little prolonged. But i always get ewcm before af shows. CM before af is due is not a sign of pregnancy, i read up on that b/c i was always curious of that too, if it could be a sign of pregnancy. Don't be discouraged about you bfn, it might just show up later. Good luck!
i had ewcm last month about a week before i started my period but cm is a hard thing to go off of because it is different for everyone