Being on the computer hours on end can give you a headache, especially if you're stressed or anxious to begin with.
I don't know exactly what Excedrin is.. but it sounds like you could have a low tolerance to it, or possibly even are allergic. Don't take it for a while. You might even have a 'bad' batch or something, for all I know.
Get some sleep--some real sleep, 8 hours minimum, you could be stretching yourself thin with Whisper--and have yourself some tea and a tylenol or motrin, something like that. Those usually relieve the headaches. I'd let the Excedrin get out of your system, first, though. If you're having a bad reaction to it, who knows what might happen when you add other drugs to the mix.
ETA: spacey and hyper are caffiene symptoms. How much did you eat before you took them? If you're going to have anymore.. take them on a FULL stomach.