Yet another bfn

So just over a week ago i posted some confusing tests 2 bfps and 1 bfn i was testing wayyy early so decided i would not test again until 3 days after my missed period today is here im three days late no real cramps i just feel full, boobs are killing and my cm is white/cloudy and a fair bit of it to the point yesterday id swore my af had arrived a few times. So today when shopping i bought a test just a cheapie from morissons obviously its not fmu i have used for this test but heres my bfn. Anyone any ideas to what could be going on?