Lost all my notes today

Hello I lost all my notes today. I read some threads from previous posts questions and answers whatever and they said to make sure it was turned on on your phone and mine was. They all just disappeared !! I have hundreds of work related notes that I need desperately how do I get them back? I just upgraded from seven something to 9.2 whatever the latest is. And my phone is going back to the homepage over and over again when I'm on an aap what's up with that? Please PLEASE someone tell me how I can get all my notes back..