I Was Just Told After Wearing A Ring At Night

I was just told after wearing a ring at night that my oyxgen dropped to 75 Im waiting on a sleep study
and an appt with my dr. He is putting me on oyxgen at night. Also my heart has really been racing keeping me awake at night. My T3 and t4 are very low but not low enough for meds. I have recently wore a heart monitor and waiting on results. I have a stress test scheduled for Feb 4.. How seroious is this and should I curtail my exercise?