I've been taking two tablets of Guaifenex PSE 600 twice a day for...

I've been taking two tablets of Guaifenex PSE 600 twice a day for 3 days and today is the last time I do. I have the flu and so I should be getting plenty of rest, but as tired as I may be, I haven't gotten more than 4 hours of sleep a night since I started this. Normally I can sleep 10 hours at a time with no problem, but I haven't gotten to sleep before 5 am since I started this medication, I wake up 5 or 6 times through the night and can't sleep past 9, latest. I have never had a reaction to medication before, this is absolutely ridiculous. It's clearing up my congestion but not letting me get the rest I need to get better, so I've just ended up sicker than when I went to the doctor. I'm not pleased at all.