Time Machine Indexing Backup has been taking an extremely long time following a Single User launch. How can I fix this?

My MacBook Pro has not been launching properly and in addition has suddenly gone to a blue or white screen countless times. I am preparing to take it to the apple store but first I need to back it up as I have not done so since two weeks ago. In order to make it start properly, I launched the computer in Single User Mode, then ran time machine. It has been about 15 hours and time machine still says that it is indexing the backup. How can this be fixed? Surely it shouldn't take this long. Thanks in advance.