How do you know if you regret a choice you made?

you'll know

You can feel it in your stomach. Then I panick

post gut feelings

When the consequences happen

A whole lot of dwelling on it.

A deep pit in my belly

Anxiety kicks in

The feelings of regret will be present, sick stomach, panicked, unsettled.

Nietzsche says regret is self-betrayal. Your past self made a decision and you should be faithful to that.