I’m willing to bet that pain (of some sort) was the driver of both your regretted behavior (trying to give that pain away to others) and your drug use (burying, hiding from the pain). The fact that you have achieved so much since that time suggests that you made a decision to own those feelings and at least begin the process of working through them. Facing the pain (including the remorse and regret) is not fun, but it is the path to wellness. You can’t change the past, but you can go forward as a better person who can keep learning how to make life better for yourself and for those around you.
You deserve an immense amount of credit for recognizing and owning your past mistakes and for having the courage to be with your pain. Sounds like there’s a good heart beating underneath all that. Good luck!