have something on one’s mind

(verb) to worry about something, to think about something a lot

Example Sentences:

A: What’s wrong, Shawn? Do you have something on your mind?
B: Yeah, Mark. My girlfriend is pregnant and I don’t know what to do!
A: Oh, man.

The teacher asked the nervous student if she had something on her mind.

Note:

We do not use this expression in the ing form.

I have something on my mind.
I am having something on my mind.