stress making AF late!!!...

Ok so I was supposed to start last Thursady and still have not.  We are ordering from our donor the day I start so that we can do the IUI on day fifteen.  I don't know how not to think about it or if maybe AF is never going to come because I have stressed myself out so much.  I am cramping but no AF!!  Really stressed and looking for words of advise on how to relax or if it is normal to skip a period if I never have before.  Thanks ladies!!