I went to a clinic and got a pregnancy test done, it was positive. i went to the er. they did a blood test and it was negative. could i be pregnant?

Great question: The sensitivity of tests can vary a great deal. This results in what we call false positive and false negative results which vary with the sensitivity and specificity of the tests. In a case like this I would repeat the tests in one week. That will usually result in both tests agreeing. Either way, be safe and follow healthy guidelines. Good luck!