That was me just two weeks ago. I had been doing treadmill time at the gym, and when I stepped on the eliptical, I swear I was going to fall over dead after the first 5 minutes. Somehow I managed to push myself to 10 and my legs were jello. Afterwards I did 20 minutes of treadmill time. I kept doing as much as I could and adding the treadmill. Now I'm up to 35 eliptical minutes. I'm hoping to hit 40 this week.
It will get better. Keep at it