If your lmp was Nov 29 even a cheap test should pick up on it by now, unless you ovulated REALLY late. As tarajanes said, get a better test, even an equate brand from walmart is better than the dollar store cheapies. Just becuase you have missed your period and having "symptoms" does not necessarily mean you are pregnant. Your body could be having difficulty ovulating for whatever reason and the symptoms are your body TRYING to do what it is supposed to but not succeeding and your hormones getting out of wack. This past summer I went 64 days without a period for no known reason, I had "symptoms" as well. I eventually started again. Just one of those flukes in our bodies :)
Try a decent test,or ask your doctor for a blood test.