My physical therapist gave me this little "excercise" that may help.
You take a crazy deep breath. Then you blow it out as slowly as you can. I mean, blow it all out! You will feel like you have to take a breath when you still have a ton to blow out, but stick with it. It is suppose to get out the bad air that can hang around in your lungs for years and expand your lungs so it is easier to breath. I think it is suppose to help with the pain too.
Anyway, do it a bunch of times but take a break and breath normally in between.