I am so very sorry that he called it quits. This is all about him and yes, something was missing in him, not you. He will not find another woman who was as kind, compassionate and generous as you were. If he didn't think this relationship would work out, he should never have included his little boy in the mix. Now, there are two children who will be hurting and two adults who will be trying to find their way.
I do not think he was ready for a long term commitment. He always seemed to have something to do that did not include you in it. He had been pulling away for a while with excuses of having to do things. As long as he lives w/his mom, he will not ever understand what it is like for someone to work a job, take care of themselves and their children, as well as keep a clean house. I may be wrong, but he seemed to be distancing himself more and more as time went along.
Whatever his reason, pick yourself up, dust yourself off and know that you are a wonderful person who deserves to much more. It's his loss if he can't see what he had.