If i stop taking adderall (dextroamphetamine and racemic amphetamine) after 3 yrs w/no break, will i go thru physical withdrawal symptoms? i take 40 mg per day, prescribed to me.

No: There is no withdrawal syndrome known from stopping amphetamines or other stimulants taken in proper dose, even for many years. What will happen is that, if you still need the stimulant for underlying adhd symptoms, those symptoms will gradually return over several days to weeks. Those abusing stimulants in high doses may experience a "crash" with fatigue and incr. Appetite after stopping.

A bit likely: Everyone differs. Doubtful it will be uncomfortable--but there's always a chance. If you are being supervised by someone who knows you, the odds can be reduced greatly.