Thanks for your interest in your health.
The question is that do you have ADD? If so 
Dexedrine is a highly addictive drug, that can cause serious psychiatric problems as side effects. ADD, 
Attention Deficit Disorder and ADHD, Attention Deficit 
Hyperactivity Disorder, can be safely treated by a drug called 
Atomoxetine, nowadays. Therefore Dexedrine, according to me should be stopped and replaced with a safer alternative. The drug 
Abilify (an anti-psychotic), also called as Aripiperazole, is given to calm down and pacify a person who ordinarily has full blown side effects associated  with "uppers" (You mentioned "Crashing") like Dexedrine.   
You should be "feeling" the way you used to feel before you began taking 
Dexedrine. Please stop taking it, when so many safer, easier alternatives exist. 
Please feel free to post any more queries.