If you are lucky, only the recent changes will be lost and you can open the last saved version using File > Open..., then see Remove minor corruption by exporting
Without full information about your version, OS, file history and what you are doing it's impossible to offer much else in the way of advice to keep it from happening again.
Sorry, I'm not tech savvy person at all and I'm in huge trouble here and super stressed...
The situation is similar to this:
The only exception is that my file was created with InDesign CC (2015) and that is the only version I have worked in. I have OS X Yosemite and the latest iMac.
Do you know if there really is a possibility to send my file to Adobe and see if they can convert it to IDML? Or what can I try to do otherwise?
Thank you so much for your time,
Did you manage to get a solution for this? Same thing happening to me and its a killer!