I'm not a doctor, but I think recovery time might depend on how heavily and how long you were drinking before you quit. If you'd been getting fairly drunk a few times a week for 3 years you'd probably be back on your feet sooner than if you'd been getting blackout drunk every day for 15 years. There are also emotional factors such as what started you drinking in the first place. In my case, I was self medicating for an anxiety disorder, so my dependence on alcohol was much more emotional than physical. I was tired all the time for about a month after I quit, then I started feeling more energetic but also more anxious. I started therapy and antideppressants and since then I've been functioning much better both mentally and physically.
There are a lot of variables so you can't always know what to expect in recovery. Just be patient, keep working with your doctor and if you think your lack of energy might be related to depression or anxiety talk to a therapist about it.
EDIT:
Pinkcuda, thanks for posting that link. If anyone else has tried GABA I'd like to know if it has helped.