I don't think you are pregnant because if you are having cramps on and off like that im pretty sure that is a sign that you are going to start your period. it seems like its around that time for you anyways. If you have had several neg tests at this point i would say its safe that you arent. But if you still dont get your period after a week or so then take another test. If still negative and period refuses to come THEN I would say get a blood test. : ) good luck!
I think your best option is to go and have a blood test. Most tests can tell from the day of your missed period, but sometimes there isn't enough hormone in it. Also try to use your first urine of the day. But I blood test will pick it up, so if you are, that's the best way to find out. Or you could wait another week and re do the test. Are you trying to get pregnant? If you are, congratulations. I hope everything works out however you want it :) good luck either way sweet. X