My MacBook air won't load past a grey screen

Hi guys about one week ago was when I used my air most recently. I turned my air on today and when I click my account it i type my password and then it takes me to a grey screen with a loading bar and loads barely anything on the bar and then my computer just shuts down. Tried multiple times. When I log into the guest account it works fine I can browse the internet as normal. I tried some test thing were it searched my computer for about an hour and then said no problems were found. I don't use time machine or have any back ups from what I know of. If I somehow have to wipe the computer clean is there anyway I can pull the information off my computer and save it all to an external hd? (Even though I cant actually log into my account Where the info is stored)

P.S. Not sure which OSX I am on if that matters.