End of the month and no period... HELP

So its the dreaded end of the month, and my also very dreaded, period, has not made its monthly visit. Now before i jump to "am I pregnant" i do have to mention that this month has been so stressful. My weight has fluctuated between 112 - 121 in just ONE MONTH. But along with the weight change from my stress, i have been wanting to eat more, needing to pee more and being restless all night.. Last month my period came around the week of the 17th. This month, i hit "my period is late" THREE TIMES. i have taken 3 pregnancy tests of which all say negative. I am thinking my levels arent high enough yet? But when will be good to test again? I swear i am pregnant and i keep pressing on my stomach to feel if i am, if thats even way of telling? Hoping my period shows up soon.. Help please!!!