Just curious, what makes you think you’re only getting REM?
Speaking as someone dxed with narcolepsy, a sleep disorder where you get a disproportionate amount of REM. There are a lot of conditions–sleep disorders and otherwise–that can cause excessive sleeping and daytime fatigue.
Not to say that it isn’t sometimes just a matter of sleep habits or consistency, but my advice is that it can’t hurt to speak with a doctor about your symptoms if you have the chance. :)