I can't say what would cause it, but abusing stimulants--even if it's "just" ADHD meds--can cause permanent changes. If your previous overdoses changed your response to the drugs--maybe even had your body react to them as it would to an invader--then you could actually have developed a sensitivity where one didn't exist before.

You do need to go see your doctor about this. The symptoms you describe are pretty far into the "unacceptable side-effect" category.

I know it might sound weird, but have you tried drinking coffee? It does work for some people with ADHD; and caffeine is a stimulant just like ADHD meds are. You'll have to go caffeine-free on weekends to prevent developing a tolerance and losing the effect, though.

If it turns out you can't take medication, have you considered an ADHD coach? Someone trained to help you organize yourself--like a personal secretary and skills trainer in one--is often a great help, whether your ADHD is medication-resistant or whether you're on meds and need additional help.