M.G.
With my first attempts at pregnancy, I'd be late and wouldn't be pregnant. Didn't make sense to me either, but it could be a week off. I think the stress and excitement over trying to get pregnant made me be a bit late. I remember doing the tests and getting upset. Which again, can make you late.
I would stop testing, test again in a week and then let it go this month if it's still negative.
Hopefully it will happen for you soon :)