vyvanse is making me super sleepy.

I took my vyvanse 40mg today and I slept 9 hours last night. I've drank enough water and eaten today and I just get super sleepy. so much so that I want to take a nap. I just started this med like a month and half ago I went from 30 mg to 40. I can't get out of bed all day even though I'm well rested, fed and hydrated.