It's all my fault

So, today my son says I wanna go to my dads this week and I asked why...he said cause they let me do more stuff there.  I told him that he can't use that against us anymore because we have a kinect and fun games for us all now and I reinforced that discipline is better parenting..which a 5 yr old doesn't understand or respect at this point.  He asked to call his dad and I hesitated but decided that I can't punish him for his dad's mistakes.  He called and got voicemail and left a message saying just pay us gas money daddy, come and get me, it's not that hard.  He then hung up.  Ben then got upset at me for not just taking him there.  I told him we don't have gas to drive 6 hrs-12 total for the weekend and that if his dad wanted to help we could talk about it.  Ben told me that it's my fault and I should take him there.  He thinks this is all my fault.  I explained that his dad hasn't reached out as nicely as I could without saying, hey by the way, your dad doesn't care about anyone but himself.  Ben defends his dad saying that he works all the time and since I don't, I should take him there.  I work too, ben just doesn't want to see that.  I'm so guilty and overwhelmed for letting this happen.  It's all my fault for ever screwing up in the first place.  If I hadn't I wouldn't have Ben, but I can't bear the thought of putting ourselves through this for another 13 years.  I am being strong and making his dad take responsibility, however is it really benefiting anybody?  I'm so confused and tired of believing that things will change and seeing nothing.  I trust God with our futures but I really need ben to have stability.  How do you make yourself look good and explain that you're being the good one without trashing the other parent?  Legally, I am doing everything by the book, realistically I'm a hot mess!  When will it end?  Let this be a lesson to anyone having premarital relations...STOP!!  It's not worth the instand gratification.