I am 54 years old, african, my pulse rate varies from 75 - 41 especially at night, what should I do? I am hypertensive and medication

See physician. Sleep apnea is reported as the number one cause of hypertension. One of the characteristics of sleep apnea will be a fluctuating pulse at night. I would talk to your physician and see if a sleep study for sleep apnea is in order.
See below. What medication(s) r u taking for your blood pressure? Is your BP controlled with those meds? Is one of them a beta blocker like metoprolol? Do u feel dizzy or faint when your pulse is below 75? Suggest u see doc to discuss meds & this side effect (beta blockers can significantly slow heart rate; if u tolerate it, ok; if not, med dose or med needs to be changed).