Thanks for your post. It seems that the psg and MSLT were both performed, was there any mention of REM sleep either during the overnight or during the MSLT. I see that you slept during the naps,however, the important distinction here is if it was sleep or REM sleep.
The treatment you received is in line with options for treating narcolepsy. Everyone has different effects when taking xyrem and sometimes it is a choice between dealing with the side effects or the disease. Wt loss is a big deal and especially if you do not need to lose any. Milkshakes work well for weight loss by the way.
I am also curious to know if other neurological issues have been ruled out. have you had an MRI of your brain and cervical spine and if so was it done with contrast? How about an EMG? Have you had a complete neurological examination?
There is certainly something else going on here beside narcolepsy and it is important to get results.
Best of luck