I was ment started my period Monday 16th on the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a>

also on

My calendar app was ment to be 10th

My days x app was ment to be 19th

Period diary was ment to be the 17th

it is now the 20th and I am still no sing of my period I know I am not pregnant but at least one of these apps have the correct date but none of them are correct this month why has anyone else had this problem please help