MAD fixed my sleep apnea but symptoms stayed the same

Short backstory: I can't remember I actually ever felt refreshed from sleep. I felt like I hadn't slept for 2 weeks when I woke up sometimes. This led to me having a lot of trouble getting out of bed, but it would get okay after a while. When I started to get this feeling every day, and I had persisting tiredness during the rest of the day I finally had a sleep study done. My doctor had also ruled out other factors and blood work.

I got diagnosed with mild sleep apnea (AHI 11) where my saturation stays fine. Got an MAD in February and I was very hopeful. However, after two months I would still wake up unrefreshed and remained tired during the day. I would get 8+ hours of sleep every night with MAD, but still fell asleep during a presentation at work. The MAD had 4 different settings, where I got jaw pain from the furthest one but could sleep fine with the 3rd. I also tried it on and off for a few nights, but I never felt any worse when I didn't wear it. I started feeling pretty bad and I guess a bit hopeless. Got a control sleep study done with MAD where my AHI was only 1,5. When I stopped wearing the MAD, I actually felt better than the period before (although it got worse again after that).

I am now getting referred to a neurologist/somnologist (appointment at the end of June) and because my wedding is in 2 weeks he prescribed me modafinil. I feel pretty good with it, although it takes about 2,5 hours to work and it wears off when I get home from work. Afterward I do notice a little anxiety related side-effects and some rebound where I feel overwhelmed again.

I'm wondering if there are any people here that are or were in the same boat as me? What ended up being the cause?