Still no AF, should I test now?

Lei
my AF was due to be here on the 28th, and still hasn't arrived! I took a test the day before AF should of arrived and it was a BFN, do you think I should test again tomorrow? Or do I wait longer?
​I haven't had signs of AF, apart from a few cramps here and there that only last just a minute or less. My nipples are very slightly sensitive, I've been a bit gassy, I did have Lower-back pain at one point (it seems to of gone now) and this may be TMI... But my cm is... Different I think? Normally before AF comes my cm is thick and creamy, but my AF is 3 days late and the cm isn't like usual, it's more like a milky/transparent lotion (sorry for TMI). Anyone else experienced this?