Tolerance to dexedrine...please help?

I got put on dexedrine a year ago. I was up to 50mg daily by the end of the school year, and that was not enough to give me any effect. (my body gets used to any drug very very fast it seems).

Dexedrine is a stimulant, and the pharmacist told me that people will sometimes go off of it for a couple weeks to renew the receptors or something like that.

I have been off of it for two months (May and June). I am still really struggling without it. I was going to start taking it again the beginning of August, so it would have been a three month break. But like I said, struggling. So I currently have 20 mg in my system that I took two hours ago.. and feel nothing. After a two month break.. it's just like teachers who stop drinking coffee in the summer right? So it will wake them up when they go back to work.

Now what?? Should I see what my normal dose of 50mg will do? Should I wait another month, but would one more month even change this? I don't think so.Or should I wait two more months? But I just have this feeling that it just wont help.