fluctuating blood pressure with high pulse rate

recent days i am having high pulse rate in the morning in the range between 83-90,i am not able to tolerate.sometimes pressure goes down 88/55.but in the evening my pulse rate is in the range 78,but sometime blood pressure goes high with diastolic pressure 90 or above.last week i had blood test ,ekg taken,doctor said everything was normal,i dont have heart disease.sometimes i do feel pain in the chest muscles and feel tired most of the time.i keep eating and drink liquids.please suggest what is the reason for this fluctuating bp and high pulse rate,body weakness.i am 118 lb height 5.6.sometimes i take magnesium tablets and my pulse rate slightly comes down for a short while.all these symptoms are happening for 4 weeks.