What Causes Low Heart Rate While On Losartan And Levothyroxine?

My heart rate is, periodically, in the range of 35-40 bpm. I have an Apple Watch which indicates this occurs about every 3 to 5 days. My blood pressure machine, a new one from Omron, recorded it at 35 bpm one morning about an hour after I got up. I checked again and it read 37 bpm. I was unaware that my Apple Watch reads and records my heart rate about every five minutes. Checking back, I learned that it is not a new thing. My blood pressure is normally in the range of 140/77. I take 100 mg of Losartan daily. I also take 150mcg of Levothyroxin every day. My resting pulse normally in the mid 60s. I am sometimes lightheaded when I stand up, but only briefly. I m 71 years old 5 7 178 pounds. I workout for an hour at least twice a week including weight machines and 30 minutes on a recumbent stationary bike.I am having a physical exam in three days.