I keep getting severely lightheaded and out of breath frequently. My heart rate drops into the 40's

I keep getting severely lightheaded (not dizzy) - it's an almost drunk feeling. Also I'm getting out of breath frequently. My heart rate keeps dropping into the 40's (lowest I've caught it 44), and my blood pressure also drops (lowest 90/46). The doctors ruled out a lung clot with a chest CT. The stress echo test showed an "unusual" slow heart and drop in oxygen levels, but everything else was normal. Head and neck MRI was also normal. My doctors have given up and referred me to Mayo Clinic.
Before I go, should I try to stop taking my pain medication? I've been on norco 10/325 (4x day) and dolobid 500mg (2x day) for 7 or 8 years to treat chronic muscle pain.
And, do you have any ideas of what is causing the lightheadedness, shortness of breath, slow heart rate, low blood pressure?
This all started about a year ago, with once in while symptoms. Now it's happening several times a day.
My acupuncturist noted my heart rate began be to slow (below 60) about a year ago as well, when I began complaining of increased fatigue. I see her at least monthly.

I am a 38 year old female, average weight.

Overall, my muscles are in very poor physical condition as pain prevents good exercise. I can do Tai Chi for a few minutes several times a week.  During the echo stress test, I could get my heart to only 135bpm before I almost collapsed.