I dunno. It sounds to me like you're overtrained, or just mentally tired of spending so much time on the bike. 200+ kms/week is a lot of cycling... what are your goals, racing? (If you turn pro, you'll have to give up the ephedrine. )

I'd suggest putting some more effort into trying to understand why riding has become drudgery and address the source of the problem, rather than finding a stimulant to allay the symptom.