Need your opinion....

For a little over a week now, I've been having lower back cramps just like what I feel when I'm on my cycle.  I've also had a queasy stomach at times, but have not thrown up.  Yesterday, I had slight discharge, but so far none today.  Could this been a sign that I'm pregnant?  I don't, however, have sore/enlarged breasts like most people seem to get.  
I am due to start my next cycle on Mar. 27.  I did take a test this past Sunday, but it was negative.....could I have tested too early?
​Also, I am supposed to get my hair highlighted this week.  Should I cancel if I might be pregnant?  Or, will it be okay?  Any thoughts or advice would be appreciated!