ADVICE PLEASE NEGATIVE TEST MISSED PERIOD?

I was due on my period on the 9th of june, when I was to days late I took a home pregnancy tests, which come back negative, I've been reading online and these test are pretty accurate, the only feelings I have had is cramping,when I smoke I seem to get headaches and when I first wake up and fluttering in my stomach which is due to nerves I think, could any one help please ???