Complete symptom relapse after 1 week

Has anyone else experienced symptom relapse after an initial phase of euphoria from treating their apnea? Was diagnosed with AHI of 8. I started using CPAP and had a solid week of feeling INCREDIBLE. No daytime sleepiness, great energy and workouts, pretty much felt like a god. Then, it slowly tapered off and I eventually ended up feeling the same as I did before I started. The strange thing is that this same exact thing happened to me when I received my custom MAD. I felt incredible for a little over a week, then slowly returned to my pre-treatment level of tiredness.

What on earth could cause this? Has anyone else experienced this?