Thanks for your question. It's hard to say why you would be yawning more than usual if you are getting an appropriate amount of sleep and feel well rested. It is quite possible that a person can develop reflexes that can be triggered by certain events, and it is possible that, for you, breathing deeply and yawning seem to be linked. As for why people take very deep breaths, it can be that your brain somehow is recognizing a need for increased ventilation, and is attempting to help you get that by taking deeper breaths without you even thinking about it. There are likely other possible explanations as well, but you would need to speak with your doctor
about this to help explain it clearly and get you the answer that you need. He or she will have many other questions that will need answers before they can understand this fully, and they may need to do some testing as well. A pulmonologist
may be a good place to start, as they can best test your lung function and capacity. Additionally, they can ask questions about respiratory problems most effectively. Please speak with your doctor about this question.