I accidently took (2) 300mg wellbutrin this morn.

I could not remember if had had taken the pill..so i took another (600mg SL). I have had a headache, neck feels stiff and flu like symptoms. Also, a little nauseated..not much of an appetite. I still am not 100% that i took two..but it just dawned on me that perhaps that is why I was not feeling well at all!! If I miss a pill then it takes two days to feel right again (very agitated) I guess I better get a new system for pill taking!! Please commit on the side effects