My Computer wont Boot up!

SO I am getting the grey apple screen upon starting my computer, it begins to load and almost completes and it shuts off (screen black, power off). I have NOT backed up to time machine (i know, i know!). My main concern are my photos. I have tried disk utility (Macintosh HD - listed first) verify which leads to a prompt to repair which results in "Macintosh HD cannot be verified completely." The "Macintosh HD" is listed a second time under the first - this one does not allow me to repair disk and once I try to repair the first this disk becomes unmounted and appears to be "read-only." The computer will not start in safe mode (holding shift). I do not know what most of this really means and would love some help! How can I save my photos from being lost??