Thanks for your question on Health Care Magic.
I can understand your concern.
No, doxycyclin can not cause breathing difficulty or panic attacks.
In my opinion, you are not improving because you are not taking correct treatment for
bronchitis.
Ideal treatment for bronchitis is inhaled bronchodilators and inhaled corticosteroid (ICS).
Without these drugs, it's difficult to control bronchitis.
So better to
consult pulmonologist and get done clinical examination of respiratory system and PFT (Pulmonary Function Test).
PFT is must for the diagnosis of bronchitis. It will also tell you about severity of the disease and treatment of bronchitis is based on severity only.
So consult pulmonologist and start appropriate treatment. Don't worry, you will be alright.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.