Stop freaking out and take control of this situation! Stress can mess with your body and cause you to miss your period. I don't know your age, but if you're young your periods probably aren't regular yet anyway. Two negative tests mean it's probably negative (though when I took them and wanted to be pregnant I kept going back for tests hoping the results would change). Your tummy doesn't get "hard" for a long time- a couple of months. Even then, it's probably constipation rather than baby (a common side effect of pregnancy. Don't know what else to say other than trust your doctor's results and preoccupy yourself with something else to ease your mind's worry. Good luck