Bfn but no AF?!

So AF was due 16/9 but I have been feeling different, like I might b pregnant for about a week now. So Monday (15/9) I took a test, bfn :( had really bad cramps, moody, horrendously sore boobs so figured was AF on her way. Now three days later still no sign of AF and my cramping has stopped, just now feel really tired! Has anyone else had anything like this? I'm going to give it a while longer and test again just wondered if anyone could relate/ offer any insight? Thanks in advance baby dust to all!! Xxx