I have just had only my second peak on my clear blue fertility monitor after six months of using it. It's therefore definitely capable of detecting it but it just hasn't apart from now and once three months ago. I don't think it's a case of missing the surge as last time I had strong OPKs for two days. I have regular(ish) periods from 25-33 days... Is it likely that I am not ovulating every month? I don't temp due to poor sleep and irregular times getting up.