This idiom or expression means:

Crazy or wild about something, usually in reference to being in love: I’m head over heels in love with her.

This idiom or expression means:

Ending in a crisis.

The health care issue is coming to a head. We really have to come to an agreement soon.

This idiom or expression has to do with:

Thinking.

If you’re using your head, you’re thinking.

A. I hear you’re going back to school again. I’m glad you’re finally using your head!
B. Yeah and I’m getting a headache, too!

I said "No" to them.

Don't attract unnecessary attention to yourself.