STRESS HAS ME LATE!

For the first time ever my period is late, I'm more than 100% sure I'm not pregnant buy this past month has been so stressful & it's the reason why my period is late....any idea when it will start? I haven't had any cramps & my period is like clockwork I start to get cramps 5 days before then my period comes....but I've had no cramps at all no pain at all nothing....is there something I get over the counter that will soothe my nerves? & how late can my period be if I don't get my stress level down?