Ferrett is correct in that Wellbutrin has the effect of increasing REM latency. In most studies by an average of 22 minutes. It would not surprise me if the MSLT did not show REM episodes. The standard nap time for an mslt is 20 minutes. The Wellbutrin may have had the effect of suppressing you REM sleep enough that it did not show on the MSLT.
In addition if your Physician still suspects Narcolepsy there is no need to wait a year to repeat the study. Your physician may do a peer – peer review with the insurance companies medical director and explain that the results may have been affected by the medication and she can then get permission to repeat the test.
AT any rate you will also want to get those PVCs checked, multiple abnormal beats in an otherwise healthy person are NOT normal.
I certainly wish you the best and please keep us informed on your progress and response to treatment