AF 21 days late now....

I am now 21 days late with the 5th negative pregnancy test and I think I give up ladies!! Isn't missed period suppose to be a sign?! I don't get it! Finally have bad nipple pains and that's about it. My cycles are usually 29 or 31 days and this one is now 51 days. I've completely skipped this months period. I don't know what to do anymore. Missing my period like this and still getting negatives has completely discouraged me and my fiancé.