Honestly, If I had the chance to go back in time and change anything, I would have gone to when I was 12 and told my parents that I loved them. And if they still died I would have changed how I dealt with my depression. But, you can't do that unfortunately and you have to live with your mistakes.
I hope you don't beat yourself up over this. Parents forgive a lot worse. Believe me I know. They know you loved them as they loved you & still do I'm sure. So please don't worry. They would want you to be happy.