Ashlee,
Lethargy is part of the withdrawal. The dark cloud should begin to lift away; every new day is better than the one before.
The duration of post-withdrawal malaise depends upon a lot of things . . . how long you have been taking the meds, dosage level, etc. But you will feel better. To quote a Biblical passage, "In your patience possess ye your soul."
Each time I quit, I notice that different things bother me. For example, after a previous WD, my lower G.I. tract was very "sensitive" for weeks." Other times I felt depressed as well as tired. But fortunately it wasn't permanent.
I'm into day 5 of WD from a low dosage regimen of HC (7.5 - 10 mg / day). It should be a piece of cake, except that I've been taking them for years. One of the reasons I kept taking them was that they stabilized my stomach issues. I told that to my doctor, who originally prescribed them for pain (I have pain from surgeries and other stuff) and he didn't object.
There are people who recommend "detox" in the form of catharsis, or fasting, etc. IMHO, the "problem" with this approach is that it is not a matter of toxins floating around in your bloodstream or G.I. tract. What has happened is that you have flooded your brain with opioids and endorphins, and it reacts by producing less of its own. Once you cut off the meds, the brain has to play catch-up to start producing normal amounts of those happy neurotransmitters. I the meantime, you feel like crap.
The thing that works best for me is exercise. Get your heart rate up and the body produces its own endorphins (e.g. runner's "rush"). It's natural, and it'll make you feel normal, at least for most of the day if you do it early.
Another thing I recommend is to visit your MD for a physical. Make sure that your liver, kidneys, and blood show normal chemistry. E.g. if you WD on top of anemia, it amplifies the bad feeling many times over.
Go outside and appreciate the beauty you can now see with freshly-opened eyes. It will reinforce your resolve.
Good luck.
Buzz