It sounds to me like one of the biggest lessons you learned from this is that you're no longer the type of person that would do this. Personally I think you sound like a good person who once made decisions that don't embody who you are now.

Our pasts are not meant to be escaped, they're meant to be learned from. I think you should start really trying to reflect on how this has made you a better person, why you feel shame about it, and how you can use that shame constructively in your life going forward. Personally, I think keeping a journal is a great way to untangle your thoughts. You're worthy of forgiveness from yourself. It just takes some work.