Those on stimulant medication how long did it take for the side effects to disappear?

I have been on dexedrine for 3 weeks for adhd but the side effects have been intense.

I can't get any sleep, my heart is often racing at rest, I have headaches and nausea. I can't see my psychiatrist again for some time so I saw a doctor who just told me the side effects will go away after a few weeks as my body adapts to it. But that was two weeks ago and I am still taking a relatively low dose of 20mg a day that hasn't given me any benefit because whenever I increase the dose the side effects get intolerably worse.

Did anyone else experience anything like this?

I'm almost ready to give up on this medication, should I stick it out?