Hello there! Your answer to your question would be that during stressful situations our bodies become more relaxed and thus makes are breathing becomes deeper but it affects it during stressful situations because our bodies tends to tense up and it becomes shallow with less oxygen is coming in you could say and also less carbon dioxide is being pumped out...
Hope this helps :)
Here are some good ways to cope with stress: •Talk to a parent, guardian, teacher, guidance counselor, or anybody you trust about your stress.
• Exercise or take a nice walk outside to get fresh air so you can be relaxed and calm.
• Study and prepare for any upcoming tests, if you have test stress.
These are the common ways of coping with stress.