AV1
1:
REGRET + ING 

2:
 MORE NOTES:
When you are talking about finished action, you can say having said, having stolen, having done

He admitted having stolen the money.
They now regret having gotten married.

But it is not necessary to use that form. You can also use the simple –ing for finished action.

He admitted stealing the money.
They now regret getting married.
3:
Expressing a wish or regret 

4:
10 things you'll regret not doing in 10 years (article)