I'm sorry for what you are going through. I can relate that. I think all the people who are keeping remorses like us have to understand one thing that we are humans not Angels. All people commit mistakes, nobody is perfect. Some people even commit deadly sins and crimes and don't even consider it wrong then why we keep on punishing ourselves for a single mistake?
You have beared more punishment than your mistake. Your mistake won't be as major that you deserve lifetime sentence for it. Please free yourself from this imprisonment. Try to forgive yourself. Wish you well...