I didn't sleep well last night, although I slept about 7 hours, which is usually enough to feel fine. So, I'm guessing that the double dose is to blame. But, to be sure, I have to take another dose again to compare. So, I took 36mg again today. If I have another stomach ache this afternoon and I don't sleep well again tonight, then I'll revert to 18mg until I see my doctor.
I should note, however, that I felt alert as late as 11pm last night and, before bed, played what I hadn't finished earlier in the day of a MindSparke session, doing very well compared to how I've done recently. So, if I can sleep but I also stay alert, even after the medication has supposedly worn off, then I'm happy! That is, assuming that I'm not burning the candle of my life at both ends.
I should also note that I worked out last night for about 20 minutes, doing mostly weights. So, however unlikely given the short length of time, it is possible, that this contributed to poor sleep.
This morning, I took Concerta with food and I can't tell any difference so far. I feel good, although a little less vivacious than yesterday morning, a difference that I, again, attribute to poor sleep.