Why am I bradycardic now when my heart rate has always been high-normal?

[Ripley31415]

I went to the ER this past Tuesday to have recurrent episodes of chest pain (spanning 10 months) checked out. By the time I got there I had no discomfort or pain whatsoever. This has been the most stressful, heartbreaking year of my life, by far (death of a loved one and several other traumatic events in my family) so I was relieved to find out that my EKG, blood work, and chest X-ray were all normal.

The whole time I was in the ER, however, my heart rate was 55 to 60, and my O2 sat kept dipping down to 88, or 89, although it would recover with a few deep breaths. I have checked my HR several times a day at home this week and it is always 55 to 60. This HR is 30 points below my usual resting heart rate, yet the ER doc and a new PCP that I saw on Friday seem unconcerned. The PCP did order a stress test, but I don't have a date for that yet.

I am female, 55 years old, and for as long as I can remember my resting heart rate has been around 85 and it easily goes higher with medicines, coffee, for example. Throughout my life during aerobic exercise. I always had to keep my movements small, otherwise my heart rate would shoot through the roof. I was one of those kids in gym whose face flushed beet-red with moderate exertion, to the point that other kids would become concerned about me. I always chalked it up to being so fair skinned, if that makes any sense.

I am partially disabled with arthritis, so in no way am I the kind of conditioned athlete that would have a heart rate this low.

Other symptoms: extreme irritability, insomnia, extreme fatigue, shortness of breath with exertion.

I understand how an asymptomatic heart rate this low can be "okay and normal" for some people, I just don't understand how it can be okay for me. It seems like this sudden, significant change suggests that something is wrong.

What do you think could be going on? Could it be something as simple as a virus? How should I advocate for myself?

Thank you so much for your help!

[Ripley31415]

P.S. My BP always runs low-normal. In the ER my BP was all over the place as high as 135/95. Yesterday in the doc's office it was 150/95. It has never been this high in my life. I as not nervous and I was not in pain.