Ok so I am 8 days late I

Usually have a 25-26 day cycle I am not on day 33 at two days ago I had spotting and my cm was quite dry so I was thinking maybe I ovulated late and that AF was coming. Well today I had a lot of cm and I thought AF was here while at work and I was like oh fu** , so I went to the bathroom and it was just cm no blood in it at all. I took a pregnancy test yesterday it was negative the spotting occurred on Friday so yes I took it on Sunday and it was negative. What would be the reason for a such a dry few days and then all of a sudden I have tons of cm?