Hi bluebicyle. In my experience, sleeping 13 hours in a row was part of the problem leading to daytime sleepiness. It's important to get the right amount, meaning 9 hours max, in my case. Have you tried forcing yourself to stay up later and get up with an alarm? It may initially seem tough, but it's possible after an hour of getting up you may feel better.

I have had cases in the past when I was stable (or even a bit depressed) when lowering my sedating med's dose (Seroquel XR, in my case) helped not only cut hypersomnia, but even depression. I only did that with my psychiatrist's approval, though.

How too much sleep makes you tired: Are you tired from...too much sleep? - Harvard Health