Af still isn't here

Kate
I usually get my period every 30-31 days on the dot. I am not at day 39 and still haven't seen her. 
I've been tired, cranky(more than usual), tender boobs etc. 
I took a test last night when I got home from work but it was negative. 
I think I am going mad but I want either af or a positive. 
Any advice at all?