I started taking Guaifen 3 days ago and i had a hard time sleepin...

I started taking Guaifen 3 days ago and i had a hard time sleeping. The first day i felt that my heart was beating very fast and i could not sleep at all. The next night, again, i was not able to sleep even 30 mintues altogether, and during those 30 mintues, i had nightmares. I did not know that this medication can cause sleeplessness until i read the side affects. I knew there was something wrong becuase it is unlike me not to sleep, since i love sleeping.