S, I know how it feels not to understand how it could be like this. How could someone you have been with so long not want to be in your life. It is really hard to get your mind around, isnt it?
I used to think, if I could just understand, then I could let go. I could move on. But the truth is, really, it doesnt matter why. Maybe its because he found someone he wants to be with and start a new life with, maybe its because he doesnt want to be friends because its too difficult, maybe he needs some time to sort things out. But really, at the end of the day, he is telling you loud and clear that he does not want you in his life now. It is what it is. You cant reason that away.
My son is also 18. I do not put him in the middle, nor does my stxh. But, if he did, I would tell my son if he doesnt like it, he needs to handle it with his dad.
We can only control ourselves. We can only do the best that we can. We cannot expect certain behavior from anyone else. You do what you can and want to for your son. You x chooses not to. Not your problem.
Listen, I know this all happened so quickly for you. You didnt know what the heck hit you. And everyone is not telling you to let go for the heck of it. They are telling you because it is what they know is the best thing for you. We hate to see someone struggling when we know what will make the pain less.
So, Sweetie, try to do this one hour at a time, if you must. Say to yourself, before you have the urge to contact him - do I really need his help? Is it something I could handle? Soon you will see that you dont need him.
Let him blow in the wind. Make the best life for Sunshine that you can. Become the best person you can be.
When you have the urge to contact him, call a friend, take a walk, post on here, say a prayer, count to 50.
Listen, this is hard stuff, really hard. It's not going to happen overnite. I still backslide, we all do. But you really have to begin to accept that he doesnt want any contact.