Hi Mike,
Well, at 3 weeks you can't help but feel weak. You're still recovering from the surgery and anesthesia, plus the radical change in caloric input and output (malabsorption). Your sleep may not be quite yet either this early, but should get pretty good soon.
Some suggestions:
Drink all the water you can and then drink some more--dehydration is a real possibility and can lead to fatigue and electrolyte imbalance. You'll probably need to be drinking (sipping really) almost constantly.
Consume high-quality protein as you can, but don't expect to be able to consume the recommended amount. Your new pouch is tender, small and not up to the task, and you cannot absorb 100% of the protein you do consume anyway. But try (as per your doc's instructions.)
Also, try to be a bit more active every few days. Don't overdo or underdo the exercise, even it consists of short strolls at first. Just be patient as your strength returns. In another couple of weeks, you can ramp up the activity. But at 3 weeks, you just can't consume and absorb enough calories to overcome the deficit created by surgery.
So, where does all this leave you? Right on schedule. You will begin to get more energy, but may feel less than 100% for weeks or months. Some take longer than others to feel renewed zip. You won't feel beat and exhausted, just tired easily, etc. But your spirits will pick up pretty soon and provide an antidote and another kind of energy.
I know it seems like forever during parts of this process and I know we can be impatient for the "New Me" including new energy. It will arrive. For now, try to remember that some of your fatigue is good for you--your bod is using energy to repair and heal and--ta daa!, burn fat.
As Dx always says, "Your mileage here may vary," to which I'd like to add, "but you will get to your destination!"
Hang in there, Mike, when you look back, you'll be amazed at how far you've already come and the best stuff is right over the horizon.
Doug
If we're treading on thin ice we might as well dance.--Jesse Winchester