-- OK, thanks for the additional info. You're right, chances are he's reacting out of pain and a sense of loss himself.
He must have felt that he didn't just lose one parent all those years ago, but that he lost two.
He's afraid that if he lets you back into his life and his heart you'll just let him down or disappoint him or hurt him again by withdrawing.
First things first: Tell him you are sorry. Make it clear that you know that nothing you say or do will change what happened, but that you would like to have a second chance.
And then, the hardest part, is to be patient. Give him a bit of time. A couple of weeks perhaps and try again. Ask for just a few minutes - for him to give you the thing that you didn't give him back when he needed it. Ask him to be better than you were.
It is a humbling thing to do, but you'll do what you must, right?
In the meantime, you cannot make this young man the be all and end all of your life. You need to be your own person and fill your own life with purpose and goals that are not dependent on others.
To do this (and I speak from experience) start with pursuing volunteer activities. Sign up for something outside of your comfort zone, but with a cause dear to you.
Meet new people through these selfless efforts and make it a rule to "never say no" when someone invites you to go somewhere or do something.
Be the smiling face that everyone looks forward to seeing. Even if you're pretending to begin with, it will soon enough be genuine.
------- as you are, so shall you be --------
Here is a great place to find open volunteer needs in your zip code and you can probably find something that starts this week
When you reconnect with your son - and I believe you will - you will be a well rounded, confident and fullfilled woman with much to offer rather than a lonely lady who is hoping for someone to fill the void.
You see? You CAN do this. You know you have to