Am I stressed or Pregnant?

AF was due on the 18th and so far nothing.. No cramps, no back pain, nothing... I took a test and it came back negative but still no AF... I haven't felt stressed so I don't know if I am.. Lol.. Help? Can I be stressed and not know it or am I pregnant and its too soon to tell? ( can it be too soon?) a lot of people have asked me if I'm pregnant and I say no cause the test says no... Any suggestions? Thoughts? Anything is helpful.