Why do i feel extreme muscle weakness,fatigue after consuming coffee? or taking adderall (dextroamphetamine and racemic amphetamine)? shouldn't the effect be opposite?

Fatigue: triggered by a non-physiologic way is likely do to a psychological source such as depression. Some fatigue with being overstimulated is physiologic. Rapid heart rate, increased work makes people tired. I see you are also ased about the same symptoms after a vitamin, so, psychological issues come to mind. But without an exam, I can only give general information andcannot say in your particular cas