Having one part of the house, especially your master bedroom be hotter/cooler than the rest of the house can be pretty uncomfortable, especially during the times of year with more extreme weather. This could be due to several reasons including improper HVAC installation and/or insulation problems. There are several companies that offer a technician to come to your home and assess your problem at no cost to you. Most of them even include an estimate of exactly what may be wrong. Even though DIY may be a project, sometimes it's prudent to get the advice of a professional before attempting a project with sensitive costly parts such as HVAC.