MacBook won’t start with Mac OS: Mac partition disappeared

Hi I have a MacBook Pro and tonight I was updating my OS High Sierra. While updating. There was black screen saying updates needs “about 30 mins”. It remained stuck there with no progress for a long time. I turned it off and back on and now it only logs into Windows which I had installed using bootcamp. My Mac OS partition does not show. When I press the “option” button to it only shows the windows hard drive. When I tried try to restart from Bootcamp to restart OS X, it restarts but sends back to Windows. I now don’t know if my Mac OS is updating or if it’s gone and what to do next. When I press Command + L while in Windows it does nothing. If I try as soon as I restart the computer and before Windows loads, it also does nothing.

Highly appreciate your support.