Your nurse could be right. As things find their new home internally and the swelling goes away, you may have some luck laying flat. Keep moving, walking and trying to do the deep breathing exercises. As you heal and the pain goes away, hopefully you will be able to take deep breaths again. Have you tried taking some short breaths stacked together w/o exhaling? (Short breath, wait 1-2 seconds, (don't exhale) take another short breath, wait 1-2 seconds, (don't exhale), etc. Try to do that a few times to expand your lungs. Then breathe out slowly and PUSH all the air out of your lungs... using your diaphram to empty them. You will probably feel this in your stomach if you are still sore. Do this a few times an hour - like during commercials if you are watching tv. Maybe this might help.
Keep us posted,
Diagnosed with CD in 1979, many resections and meds
Perm Ileostomy July 1984 at Cleveland Clinic
Disease free since surgery