High heart rate. Which seems effective.

Hi i am having high heart rate since couple of years and doctor has prescribed propranolol tablet 10mg once which I am taking for last one year. In recent past sometimes I am having trouble while sleeping where I feel my whole body becoming numb and severe chest tightness and I wake up. It doesn't happen daily but often I feel this that too only while I go to sleep. The discomfort is so heavy that I could not sleep and as soon as l wake up my high rate become very high and sometimes I feel dizzy. Is it due to the medicine m taking as I take only tab ajaduo for diabetes which is under control. I do not have BP either. Though I tried reducing the dose of propranolol to half and one fourth to find the difference which seems effective.