I think I feel so overcome with guilt for things I've done that I don't believe I can be a good person
Well now I am curious, what bad things have you done that make you feel like such a bad person?
I used to punch my partner in the face when he pissed me off
It is important that you have acknowledged the past bad behavior so you can move forward. While you past actions cannot be justified, you are trying to do better and that is important to move forward.
I already went to couple of courses and learned to not do anything like it anymore.
It is terrible that you and your loved ones has to both go through these issues, but it is amazing that you were able to realize how wrong it was and be willing to better yourself. It sounds great that you've turned your life around!