I think I may have violated academic integrity last year - what should I do?
The past is the past and cannot be undone. Whether you are ashamed or not, you need to move on. But you don't need to invite external punishment for past misdeeds that haven't harmed others. 

It is best if you do your own work, of course, since that maximizes your learning. It is worst if you copy since you haven't really learned anything. In between is getting hints about things, with various graduations of that. The best hints come from your instructor, since s/he can give you a minimal hint to get you past a block so that you can advance. Getting hints from others is worse since those others may not be taking your educational development in to account. 

So, for the past, let it go. For the future think about the goals of the exercise, not just the end point. Seek appropriate assistance that won't hinder  your learning rather than inappropriate assistance that might. 

Probably you transgressed norms since you describe it yourself as copying. But treat it as a learning experience and move on.