I have experienced something like this. On some occassions, I could ride it out and had experienced once a 'calculation' that could never ever be explained in words. Only once could I ride it out without freaking out. It normally occured when I was in a situation where I was near a lot of people(particularly restaraunts). Smoking even a bowl before bed every night keeps it away though, and I have only noticed it once or twice since I started smoking.