I need help with my marriage on the rocks

Title: "I need help with my marriage on the rocks"  Author: Unknown

I have been separated from my husband for two weeks now, by my stupidity. I left him because I couldn't handle all of the stress that was going on in our marriage and all that around us, including his controlling parents to which we lived under their roof due to financial trouble. I need his forgiveness so bad. I never meant for all of my running away to get this far out of hand. He says that he wants a divorce and nothing can change that. He says it was my decision. He has already separated all of our stuff and given me most of my stuff, he wants to keep my wedding ring and a few things that he thinks should belong to him, but none of them even matter to me.

Only he matters to me. What do I say to him to help him see how serious I am about keeping us together? The last time I went up to his parent's house, where he's at, to get the rest of my stuff, his mother stood over him, I tried to give him a hug, but he was stiff. I want to write him a letter, but don't know where to start. Four days after our breakup he signed up for a date site and put down that he was single and looking for someone. I'm so very broken. How could he do this. How could he forget about God, about me. I've done nothing but keep God in my life closely, where as it looks like he is seeking elsewhere for love. Why? How do I fix this marriage that looks as though it's heading for a major disaster? I need answers and prayers desperately.