How to stop my notes from appearing on other apple devices?

I have a lot of notes on my iphone. But then, when I use my mom's iphone, my notes appear on her notes app. Her notes also appear in my notes app. We use the same apple id so maybe that's the cause of this. Is there anyone who knows how to stop this? Also, I connected my iphone to itunes and i saw the "sync notes" is unchecked.

You're absolutely correct, it's the AppleID. You should have your own AppleID. Your mom could set you up your own AppleID with a prepaid credit card for the payment method so there are no accidental purchases. It will give you the separate account and make things a little better.

Alternatively, go to Settings > iCloud > Turn off Notes. This will make it so Notes is not synced with iCloud, thereby not matching the notes across the devices.

You are using same apple id from both device. My suggestion is to create and use different apple id for your mom or your self.