I went to a clinic & I was told there was nothing wrong,I might have migrane & all the test are fine. In fact, I have hyper tension

I cannot tell you why the clinic failed to diagnose you with hypertension. Taking someone's blood pressure is part of a rudimentary exam, and you would expect the clinic to do that. You do not likely have a financially viable medical malpractice case, however, because your condition resolved with additional care. Medical malpractice cases are very costly and time consuming and for the most part they are only financially viable when a patient suffers a significant permanent injury as a result of the negligence.