late period

My period is now eleven days late. I have taken six pregnancy tests over the past eleven days and am still getting negatives. On top of this, for the past two weeks I have had large amounts of very thick, clear discharge- enough that I keep thinking it's my period but it's not. Is this a sign of anything? Also, what is the likelihood that I am pregnant but am getting false negatives? What else, besides pregnancy, could be causing me to be so late?