My heart rate is very volatile. without a beta blocker at rest it can get up to 150+ but with meds it stays at 50 & at night slips to 40. is this ok?

This is strange!: I am concerned about your heart rate fluctuating so much. At your age the heart is supposed to be healthy and beat between 60-90 times per minute. The doctor who gave you a beta blocker needs to explain to you why he/she placed you on a beta blocker in the first place. Intense anxiety can cause heart rate to go high especially if you have panic attacks. You need a psychologist/counseler to help y.