What on earth?! Now I'm confused

Ok so I'm 3 days late for AF but still BFN. I've changed the date of my AF on my glow and it's compleatly changed my last fertile window! So when I tried for a baby on what I thought was my fertile week, was I doing it at the wrong time??? 
​Confused and fed up. I really want another baby and my only way of doing it is with a sperm donor, but I can't afford to waste money on sperm if I'm getting confused with my ovulation.