Not to alarm you, but I’d be calling that cardiologist’s office to get in without a delay. Given the history of your mother’s cardiac arrest at a young age and your drops in blood pressure/heart rate, an evaluation is really important. Low blood pressure can be the cause of your exhaustion because your body isn’t getting enough oxygen. But your exhaustion, BP that low, abnormal heart rhythms and passing out aren’t things to trifle with.
You mentioned waiting to see a cardiologist for over a year. Do you actually have an appt scheduled?