Hypertension. Hoping for suggestions!

I have hypertension since 4 years and till six months back, I was taking Dilzem cd 120 in the morning and Dilzem sr 90 at night. Doctor gave this medicine because I also had a high heart rate that time due to tryptomer 10 mg which I was taking for migraine headache. So considering heart rate and bp , Dilzem was given. But my bp was never going below 140/90 and sometimes 150/100. So six months back medicine and dose changed to Dilzem cd 120 one morning Telma 40 one at night. Now my bp reading is 120/80 and sometimes 110/80 and 120/70. So my query is whether I should need to reduce my dose or continue the same dose. My cardiologist told to continue. But just a worry if bp would get too low. Hoping for suggestions