Anyone here on Dexedrine?

I am on Dex 20mgs a day (10 in the morning, 10 in the aft) and I am noticing that it isn't working as well as it did when I first started, it almost seems to be losing it's effectiveness? Does this happen and if so, do you switch to another med for awhile?

I was diagnosed in August by my doctor, but then we moved to an entirely different province and live literally in the middle of nowhere, so the doctors here no absolutely nothing about ADHD and their meds and the closest psychiatrist is 4 hours away with a 6 month waiting list.

I'm moving back to my old town in 2 months and I will follow up with my old doctor and get in to see a ADHD specialist but for now I have to wait, I know the doctors here won't help me, they had a hard enough time prescribing me my refills of Dexedrine and just can't wrap their heads around adult ADHD

Anyways, any thoughts or what not would be appreciated! Thanks!