Hi Dan,
Am sorry that you feel so weighed down by your past. It is good to recognise your past faults but the skill is in dealing with them - like Webgoji's advice - and making strong intentions not to repeat them. I've done many wrong things in my marriage and I'm not out of the the woods. One thing that helps me to bear the shame is to have some self-compassion. We are human, we do wrong things typically because we think the selfish way will bring happiness. It doesn't - we are plain stupid but we need to have compassion for ourselves - treat yourself like you would your best friend. I do this with an image in which I see myself above myself putting a hand on my shoulder with compassion. It definitely helps to bear the shame.