Hey guys,
Thanks for the response. I formatted the SD card again and reloaded retropie. Still had the same problem so what I did was removed my wireless playstation controllers and plug my hard drive in a different usb port (because it wouldn't boot up without the hard drive in) this time I had a different error message. I turned it off, unplugged the usb then turned it back on without the USB and then everything was back to normal. It's bizarre, but I'm glad everything is back to normal.
Thanks for your help!