Good for you for starting in on your fitness program! It does take time to build up stamina so that you can tolerate longer exercise periods, so you are expecting too much of yourself right at the start. Add in some walking/jogging on the indoor track. Work out on the machines at a lower rate of speed to see if you can stay active longer, or take rest periods and start back up again. Try some warm up stretches and other low impact activity, including swimming.

The Xenodrin/ephedra actually is dangerous to take and may be making your exercise intolerance worse because it speeds up your heart rate too quickly. So please stop taking that medication, as risks are heart attacks and strokes. If you have concerns about your overall health and fitness, we'd be happy to check you out at the Student Health Center and make sure you have no other problems interfering with your ability to exercise.