What Daisy says might sound nice, but it's wrong on science. Your body sweats more the and earlier as you improve.
First, while the elyptical is for old people with injuries, you should find a better piece of equipment.
Also, I think the real issue is you are not drinking enough. Your urine should be near clear.
As a reference, I am in awesome shape. I mean really good cardio shape. I went spinning last night for 45 minutes. During that time I drank a half gallon of Ultima. This morning I was at the track and I downed a quarter gallon of Ultima and a quarter gallon of regular water. I sweat like Britany Spears in a confessional booth. I squeezed more out of my tops this morning and last night than most people drink all day - totally seriously.
Anyway, you aren't hydrated enough. Monitor the color of your urine carefully - it should be near clear.
And don't worry about gaining water weight. Drinking water actually accelerates your metabolism.