clear blue test failed?

Girls... please help me out I'm so confused to why this happened! I'm 5 days late on my period.. I tested in the morning left it there and went to get lunch, came back and all of it is BLUE! How accurate is this? Anyone know why??? Has this happened to anyone before?? Also it's so hard to tell postive or negative! Like I honestly don't want to get my hopes up if this test is no good coming to the fact it went all blue on me?!