I have always had horrendous cramps.
When I was in my early teens my periods were normally 2 weeks long or so. Then after a few years they lessened time wise but not in regards to cramps. For me my tell tale sign is that I get nauseating cramps about a day before my period starts. I never really noticed my breathing or lung function in relation to my period but I know that on days that my cramps are horrible my daily PFTs are lower now post transplant because I can't stand to force anything with my stomach.
Cramps wise I get nausea, occassionally have gotten vommiting. I get upper leg and groin cramps that have actually caused me to almost fall over when walking. I get horrible stomach cramps and major back pain. At times I get headaches too and I most always get diarrhea. Thank GOD those things do not last my ENTIRE period but they normally last at least 2 days. All of that is WHILE on Birth Control. I have been taking birth control for the past 6-7 years. My gyn has checked most things out and all of my paps have come back normal, so my official diagnosis is just "dysmennorhea" I think is how you spell it - fancy word for severe cramps lol.
As for my period and being sick I know for me anytime I was on my period when I got sick - and thus had to start IVs my period would stop the day I started IVs .. even if I had literally just started the day before (my periods last a typical 5-7 days usually). When I started IVs my period would vanish and it would not return until about 2 months after my IVs ended. I never really understood why, but maybe just my nutritional status while sick .. who knows.
Take Care,
Lindsey