No period but cramps!

I always been having irregular period that last up to 40 -51 days. But since may I been having regular period of 34 days.. but this month havent come yet I been having mild nasuea once in a while, tender breast once in awhile. Cramps almost every day comes and goes. It been like that for like 12 days now. And no period yet..ooh I did a pregnancy test and it came negative..have this happend to anyone.