I got a wicked bout of bronchitis after my father died.
Some new agey guy once told me that severe emotional traumas are like physical traumas... you get hit and then they rise from your center to the surface like a bruise. I don't usually listen to that stuff, but I do find it interesting that so many people who've suffered losses get colds, bronchitis, and other lung ailments after the stress ends.
Anyway, I'm sure it's just the stress. Make sure someone is taking care of you while you're looking after your mom, okay?