Hi Audc,
I'm so sorry to hear about your liver and kidney disease and associated pain. I do hope pregabalin continues to be helpful with pain management.
Do not pay too much heed to negative stories on the internet - I imagine just about every medication by now has had people who have had a negative experience, and taken to the internet to warn others. On the other hand, those who benefit don't feel such a strong need to publish their experience.
As you say, pregabalin is quickly metabolized and excreted. It does not completely disappear in six hours, though. That is the half-life, so approximately half remains in the body after that time. Nevertheless, it may be slipping below the level necessary for pain management. Talk it over with your doctor. It may be possible to increase the dose, or spread it over more frequent doses (doctors usually avoid this because patients often don't comply or forget doses). Good luck continuing with pregabalin.