Well I found out why I didn't take to well to the Dexedrine, I'm not sure who's fault it was the Doctors or the Pharmacist, but I was supposed to be taking two 5mg pills in the morning and two in the afternoon but on my bottle it said to take four in the morning and four in the afternoon, so I had been taking twice the amount I should have been. Has this happened to anyone before ? I'm pretty upset about the whole thing I could have OD'd or hurt myself.

ACK, so you got it all straightened out right? I hope so.....
Never happened to me, I am very OCD about making sure my doc tells me EXACTLY what needs to be taken, and then making sure what I get at the phamacy matches that.

Taking 20mg rather that 10mg didn't put you at risk - unless you have pre-existing conditions that the dexedrine would make worse - like high blood pressure. But of course if you had such a condition, your doctor wouldn't be giving you dexedrine in the first place.
Here's a good link to a page on Dexedrine: http://www.drugs.com/PDR/Dexedrine_Tablets.html
Specifically it says about overdose:
"OVERDOSAGE

Individual patient response to amphetamines varies widely. While toxic symptoms occasionally occur as an idiosyncrasy at doses as low as 2 mg, they are rare with doses of less than 15 mg; 30 mg can produce severe reactions, yet doses of 400 to 500 mg are not necessarily fatal.

In rats, the oral LD 50 of dextroamphetamine sulfate is 96.8 mg/kg.

Manifestations of acute overdosage with amphetamines include restlessness, tremor, hyperreflexia, rhabdomyolysis, rapid respiration, hyperpyrexia, confusion, assaultiveness, hallucinations, panic states.

Fatigue and depression usually follow the central stimulation.

Cardiovascular effects include arrhythmias, hypertension or hypotension and circulatory collapse. Gastrointestinal symptoms include nausea, vomiting, diarrhea and abdominal cramps. Fatal poisoning is usually preceded by convulsions and coma."

I'm betting your Doctor made the mistake - only because pharmacists are so anal about scrips for stimulants - they have to fill the scrip EXACTLY as written, and if there is a mistake, they can't just call the doctor and get a new scrip over the phone, like they can with drugs that are not controlled. My doctor initially made a mistake with the size of the pill, thinking there was a regular release tablet in a 10mg size and the pharmacist couldn't substitute 2 5mg tabs instead - I had to pay my doctor a visit and get a new scrip.