Sleep Apnea and Anxiety

Sleep Apnea is a medical issue that is better understood by a medical doctor.  If your regular MD cannot find a physical reason for it, maybe you should get a second opinion.  While anxiety can disrupt sleep, I think it's a bit of a leap to say anxiety is causing your sleep apnea.  I don't know that you will be able to find a conclusive reason for your sleep disorder. 

You said in your question that you have a stressful job.  Does this mean you have a difficult time sleeping because of issues related to work?  Maybe you can try to improve your self care.  You said you exercise regularly which is great, but can you also take time for yourself?  This doesn't meet you need to sit in your office with the lights off in complete silence.  Can you set aside just a few minutes for yourself?  This might be something that's missing from your daily schedule and could help to decrease your anxiety.  Best of luck.