Jen, the estrangement from your son is totally consuming you. You cannot change the situation, you are unable to contact him to express your sorrow and make amends, it's totally out of your hands.
Just as with a bereavement, for your own sanity and future happiness you have to make a conscious decision to move on. Without the physical presence of your son you still have your memories of him, that must be enough for you, because until the day he walks back through your door, your life will be on hold, you have to forgive yourself for your mistake, none of us are perfect, you deserve to be happy.
Join social groups, your library will have details, I'm sure there will be something you will enjoy doing. Interaction with real people will bring you out of yourself and will help to fill the void of not having your son in your life. Walking groups are good, you'll be surprised how much you can get out of walking and talking, everyone has a story to tell, no-one's life is perfect, we all have our issues, you are not alone in your misery, but there are ways to help yourself feel happy, even in your sadness, you owe it to yourself to have a fulfilling life. You apologised to your son, he chose to disappear from your life, don't let this affect the rest of your life. Smile, laugh, have fun, you owe it to yourself. Don't wallow in misery. Life is what you make it. Take care 💐.