Q: File system verify or repair failed. Choose startup disk?

Hello,

I've been trying to install El Capitan on my MacBook Pro and receive the following error message from the OS X Installer: "OS X could not be installed on your computer. File system verify or repair failed. Quit the installer to restart your computer and try again"

When I go to restart my computer, it re-launches the installer and tries to download El Capitan again until I receive the same error message.

When I try to quit the installer, it prompts, "To quit, click Choose Startup Disk to select a startup disk for your computer. If you need to restart, click Restart."

Clicking Startup Disk prompts, "Select the system you want to use to start up your computer." The only option I have is to select  "Macintosh HD OS X, 10.10.5" and click Restart, which then prompts, "You can't change the startup disk to the selected disk. Startup Disk could not gather enough information on the selected disk."

So all in all, I'm in an endless loop of failing installations and dead ends making it impossible to use my computer. PLEASE HELP!!