"They say" a healthy amount of weight to hope to lose is 1-2 lbs per week, and if you're losing more than that you have to worry about it being muscle mass instead of fat that you're losing. At the same time "they" also say in the first two weeks of doing the south beach diet you can expect to lose as much as 14 lbs in the two weeks - but I think that's water weight your body lets you get rid of.
Are you drinking enough water with all of your gym time? I know if you're not getting enough water flushing through your system, your body will hold on to every little bit it can which can cause you to gain weight instead of losing it, despite lots of calories burnt.
As for the eplitptical - it's probably just a matter of slowly pushing your self a little bit at a time, and pacing yourself! I know with running, 30 seconds in to it and I am DONE, so I had to start with speed walking and work up to 30 seconds of running, then work up until I could even start the first week of the C25K! It's a long tedious process but it's worth it
For more help you should definitely ask people in the "calorie counter" thread. I get a lot of advice by reading those posts and I'm not even a calorie counter, so I bet they can help you a lot too

And welcome to 3FC

!