When i take half of a 5 vicodin at night seems like i dream an have nightmares is this a common complaint i only take half a day?

Depends on which: half. Keep track of which half causes bad dreams. Usually its the right. Keep a pen and pad of paper next to your bed Write down the first thing that pops into your head after a nightmare and then go back to sleep. In the morning you can go back and look at what you wrote. If it is incomprehensible throw the note away. Do not watch re-runs of recent Bruins, Celtics or Patriots games for a week