Late AF & a BFN

Im 4 days late, we've been ttc for 1 year now.. ive been having lots of cm for good week now like lots.. i thought af was coming but never did. I did have sex this morning and i got a lil bit of blood so i thought the sex was making af come for sure. But then all i got was watery clear cm all day... has this ever happened to anyone? :( trying to keep the faith!