Vyvanse making me slow, tired and stupid

The doctor prescribed me Vyvanse (10 mg) and I started it on Tuesday morning. Took it at 7 and by 10 I was a walking zombie. I was exhausted. Like an exhaustion that makes you stupid. I spent the day staring at a computer screen but not really able to do anything and the next (Wednesday) was somehow worse. My vision also went weird. Like I had mild tunnel vision and lost my peripheral vision. I really didn't like that. Today I didn't take it because I'm 2 days behind and have a financial report to have done on Friday that I can't be stupid for. Has anyone experienced this? Is the dose just too low, do I have to get used to it (I think I'll lose my job if that's the case so that's a no go) or is it just not the right fit for me? Yesterday I actually drank one more coffee than I normally do to try and wake myself up. It didn't help. Last night I was trying to make bechamel sauce and talk to my daughter at the same time. I couldn't do both things. I can make bechamel in my sleep.