This is exactly how it worked for me. Definitely a fast metabolizer too, but I felt tired with Vyvanse. So pricey too. I'm still trying to get my adult adhd meds adjusted... The long acting stimulants just don't seem to help, but the short-acting do--as long as I take them when I'm supposed to. Anyway, you're not alone. Vyvanse was a bust, as was Concerta. Don't give up.