Any ways to jump start periods?

I have irregular cycles with the shortest cycle being 23 days and the longest being 73 and everything in between.... Its averaged to 40 days though, im now 12 days late, im not pregnant, so does anyone know of anyways to jump start my period??? Ive been cramping like im gonna get it for days but nothing! Can any one help please!?!?!?!?!?!? Im desperate and miserable!