So sorry about your BFN.
Are you taking progesterone? Sometimes that can delay your period. Once you stop taking it, it may bring it on.
What will be your next step? Another IUI? IVF perhaps? (I'm stimming for my 3rd IVF cycle right now and although I was successful on our 2nd try, I also know the pain of that BFN.) Good luck to you in any future cycle you endure.