It isn't your fault hun. It is you BD's fault. Men aren't held to the same standards as we are as parents. There is no real social pressure for them to do any more than send a check once a month to support their kids. This causes way to many men run out on their kids because they do not feel it is their responsibility to be a active member of their lives. And sadly our kids are the ones who suffer for it.
please dont ever think you have failed your son that is the farthest from the truth. I grew up without a dad cause he wanted nothing to do with me and yea it was hard as a child but ive learned to appreciate my mom so much more for what she has done for me and what she has sacraficed. I am also a single mom now as well and my kids father is finally starting to get more involved after fighting for months but my kids know that their mommy will always be there for them no matter what. Your son is very lucky to have you as his mom though