Can't see HD in disk utility in recovery mode, but can in OS
This sounds like a hardware failure; based on my own experience it will turn catastrophic, and probably sooner rather than later. Hopefully you have AppleCare, but:


get yourself an external hard drive, and make a Time Machine backup immediately.
reset your SMC and reset your NVRAM - if you're lucky, this is just some intermittent / bad state in one of these components and zapping it will restore your mac to full functionality.
take your mac to the Genius Bar and describe the symptoms; hopefully they can replace any defective components, but do this after you have a full Time Machine backup!