Hi there!
A couple of things come to mind that could "wipe you out" after exercise. First, if you don't build up your endurance, and overdo your activity, you could feel overly-exhausted when you're finished. That is, build up your cardiovascular activity over time. Don't try to jog 5 miles, when the most you've done before is walk 2 miles. Go on-line for some easy to follow programs for biking, running, or walking. Or, you might try interval training, which boosts cardiovascular activity, but is a blend of higher and lower intensity activity. I'm assuming, of course, that you've been checked out by your doctor for robust physical activity.
Another problem many women have - even the healthy eaters - is not fueling sufficiently when exercising for an hour or more. For most activities of an hour or less, of modest intensity, you only need water to keep you hydrated. If you're dehydrated, you can feel fatigued. If you exercise more intensely, and for longer than an hour, you need to fuel about 30-60 minutes before your activity, to sustain your energy, and fight fatigue. Try a banana spread with a tablespoon of peanut butter, or a half a turkey sandwich - a blend of protein, fat, and carbs is a good thing. If you don't have enough fuel before your activity, you can be totally wiped out at the end of your routine.
So, set some realistic goals - and build up your duration and intensity of exercise. Also, make sure you have a pre-activity snack and stay hydrated (with water or after an hour, add a sports drink like gatorade for quick energy and salts).
Good luck, and let me know how you are doing!
