Hi, Tracy! I know that must have been really frustrating! But I think you'll find that your endurance will come back quickly. From what I've read, it takes six weeks to lose everything you've gained. After two weeks, you do lose some, but as one person said here, you get it back pretty fast. Just be gentle with yourself.
Barb, I always used to do my elliptical first too, because it is hardest for me as well. But my trainer told me that the weights use the energy in your blood. The elliptical will use the energy in your blood and in your fat. So if you do weights first, you use up the energy in your blood so the elliptical is forced to use the energy in your fat. So it's best to do weights first. She also told me that in the past, people believed that cardio was the only way to burn fat but they have found that, in fact, after one half hour of strength training, you burn fat for 12 hours, regardless of what else you are doing. It revs your metabolism. She said it is equal to the amount of fat burnt when you do an aerobics class for an hour!
She said cardio is important for heart and lung function, but if you have to choose between weight lifting and cardio (because of time contraints, etc.), go with weights.