Yes, and went to sleep shorty after my noon dose of 10mg dexamphetamine.
So they really aren't working for you at this point.
Dexamphetamine is effective for sleepiness in much the same way that paracetamol is effective for pain; if I'm just a bit tired or have a mild headache, dexamphetamine or paracetamol will completely eliminate it for a few hours, but if I'm very tired or in a lot of pain, they'll only take the edge off of it at best.