My blood pressure rate is usually 135/85. However, if I take it five minutes later it goes down to 120/72. Which one is my real blood pressure?

Both are real blood pressures, but it is impossible to say which one more accurately reflects your average blood pressure. When there are wide discrepancies in properly taken blood pressure measurements, doctors sometimes order 24 hour blood pressure monitoring to determine if high blood pressure is really present. You should consider speaking with your doctor about this option.