Methylphenidate Backorder ?

I have recently started taking this med, and i'm finding that it has been on "back order" for over the last YEAR ! When I go to fill a script, if they dont have the exact amount i need, they cant take it. I cant leave the script with them until they do, either ! I take 6 x 20mg tabs a day. which is 180 a month. No one has this amount, so i'm stuck. And because of the class of drug, i cant do mail order either ! How is the FDA allowing this type of stuff to happen with peoples medication ???? Help me, please !