A word of caution to those readers who might want to try self-medicating:

I have used pharmaceutical grade methylphenidate and amphetamines. The former inevitably led to suicidal thoughts and feelings or worthlessness at the end of the day (i.e. once the dose is gone). This happened to all of my peers who tried it. The effects were mild, but still quite noticeable. And we were healthy (both mentally and physically) young men.

My advice is you just get a prescription from a doctor. They are unfortunately quite easy to come by. At least your dosage will be supervised, and you will have someone to talk to about possible side-effects without fear of reprisal.