Adult ADHD and Adderall XR

[Sherri]

I just started taking "Adderall XR", my doctor prescribed, 2 weeks ago, I am in my 40's, I used to take "Dexedrine" (5mg) once daily, and this was in 1996-1997. I haven't taken anything since then. He told me that this is a form of "Dexedrine", this really worked for me back then, but I having some problems with my dosage on Adderall XR, because I'm taking "20mg" to start with, and after 6 hours it doesn't seem to be working for me, and I am really tired afterwards, I go to bed really early like 7 pm., to where I'm so very sleepy I cannot stay awake. I take at 5 am. and I start work at 6 am., works fine up until 11 am. I can focus on my work without any distractions, then after eating a small lunch, (decrease in appetite), I feel like its not working for me. I am overweight like about 75 pounds, so the weight seems to be coming off, which is a good thing, only after 6 hours, I have no energy. I realize I work long hours, sometimes 10 hour shifts, but "before" taking any medication, I was never this tired before, is this normal, is this medication suppose to make you so tired, or should I take a higher dosage, and will a higher dosage make me even more tired ? (very confused). "Please Help". Thanks !