I can answer your question for you:
What you are experiencing is something called TMS--tension myositis syndrome, now sometimes called tension myoneural syndrome. It is a psycho-physiological disorder which can cause numerous kinds of symptoms, including the panic attacks you experience, (your 'difficulty breathing'), heart palpitations, and sleeplessness. Yes, it is stress related.
Read the book "The Great Pain Deception: faulty medical advice is making us worse" by Steven Ray Ozanich. This book is about the work of John E. Sarno MD. Also read "The Divided Mind: the mindbody epidemic" by Sarno. Also look up Dr. Sarno on youtube.com. You will find dozens of videos about him and numerous "Sarno changed my life" stories.
In fact, go to 'thankyoudrsarno.org' to read a lot of heartfelt thanks to Sarno for changing people's lives. There is also tmswiki.org.
Learning about TMS is the best thing you can do for your health and you will be healthier and happier for the rest of your life.
https://www.youtube.com/watch?v=YDyI59gkMhE&t=407s