if you need time off work due to nightmares caused by your DID then it is interfering with your life. how much it is interfering really depends on how often you need time off!

ask yourself can i do the things expected of me most of the time, some of the time or none of the time
can i keep appointments with professionals and friends most/some/none of the time
does my condition prevent me leaving the house most/some/none of the time
am i able to adequately look after myself, my home , my pets most/some/none of the time
am I able to hold down a job / attend work/ do my job to the necessary level most/some/none of the time
use your answers to work out how much your condition is interfering with your life.