10 days late, Negative Test

Help! I am officially ten days late. My body is always like clockwork, every 28 days I get my cycle. I was due to start on April 28th but I never got my period. At 8 days late I took a digital test that said "not pregnant". We have been trying to conceive for four months and had plenty of practice making a baby this past month. Is there any hope at still being pregnant, or is my body just off?