What should I do?

I'm in cycle day 34.  And my period is not showing.  Not even crampy not spotting and my cervix is still very very high.   pregnancy test shows negative.   My cycle can range from 28-33 days.  33 is rare but has happened twice this year.         My friend says she thinks I'm pregnant but how is that possible if the pregnancy test shows negative?  Generally they are very accurate especially by now