Do not disturb on my iPhone is randomly coming on

My Do not disturb is randomly coming on when I don't want it to. For example, I have an alarm set on my phone and I notice a while later that the Do not Disturb is on. Also, it turns on over night. I had a situation where my son tried calling me at midnight to pick him up at a friends because he was scared and because my stupid phone was on do not disturb, I was never alerted to the call. I don't EVER want my phone to be on DND. If I don't want calls or alerts, I will mute my phone. How do I get this shut off for good?

Before you direct me to the DND settings - I have already gone there. My DND button is SHUT OFF! But it automatically turns itself on. That is my problem. SOMEONE HELP PLEASE!!! I don't ever want what happened last night to happen again!!! My poor kiddo was scared to death and couldn't get a hold of me!

[Re-Titled by Moderator]