Vyvanse disapointment!?

In high school I was prescribed Adderall 30 mg/day for my ADD, every thing about it was great, the effects were always consistant each day so I never had to increase the dosage or add "boosters" to it, each day I felt energized, focused, motivated, and had a nice eurphoric feeling. Last month my doc switched me to Vyvanse 40 mg stating that it's a safer and much more effective medication but the thing is so far it's been a complete disappointment. The first few days I felt somewhat similiar to that of being on Adderall which was expected since the two are amphetamines/stimulants but the downside is that I became immune to the effects after a few days and the vyvanse actually gave me the opposite desired effect consisting of low fatigue, loss of interest in things, mild anxiety, and low motivation and focus. On the days I actually feel the drive and focusing effect (usually after I take a meds vacation, typically on the weekends) it usually only lasts for about 4 hours and then I experience a pretty bad crash. I'm going back to my doc in a few days to see if he could possibly switch me back to adderall. Oh and my doc did start me out on 30 mg of Vyvanse initially but I only stayed on that dosage for about a week an half before he bumbed me up to 40 mg after I told him the medication didn't do much for me. I just want to know if anyone else has ever had this problem after switching from Adderall to Vyvanse and if they know what causes it. I know that the two have different amphetamine formulas with Vyvanse having the single D-amphetamine while Adderall has both D and I-amphetamines, could this be the cause? And also why would a doctor seem set on keeping someone on Vyvanse even after finding that it isn't effective for the person? I read on a forum that a lot of docs are highly compensated for endorcing the drug since it's still new and the manufactuer is still trying to get it established in the healthcare industry but I don't know how much truth there is to that but if this is the case how could I find a doctor that isn't swayed by those kinds of things when writing prescriptions?