Why does he have such a big chip on his shoulder after the things you have done for him? Very ungrateful! I am 26, didn't do well either on my GCSE's, so I went to college and qualified as a nursery nurse, after a few years I managed to get around the world with this qualification travelling on cruise ships and am now a manager working at home. I also just finished a A-level college course (paid for myself by working two jobs) and am hoping to go to uni next year to do pediatric nursing, aka, making things happen for myself off my own back like he should be doing, yes, help is always nice, but your son needs to wake up and realise that he can't just sit about and wait for something to come YOUR way just so he can benefit out of it (mind you, if he is like this at 31... chances are he is set in his ways and wont realise this and will continue to act like a tortured soul and a victim). Its not fair on you, it sounds like he is making you feel a bit guilty about the situation he has found himself in and YOU SHOULDN'T. He made his own choices and threw things out of the window (and decided to bring a child into the equation before having a semi decent job to provide for this child), yes, because of the way you brought him up, you have probably made him behave in this manner... but still, from very young I was given a lot of things and provided for but i was always aware and VERY appreciative of what my parents did for me and realised MYSELF what I needed to do to be able to live a comfortable life and buy myself a nice house etc in the future...
Try not to feel guilty, you shouldn't, its just a shame that your son is probably going to learn this important lesson at a very late stage in life when he could be doing things NOW to make sure he and his family are comfortable in the future... If he ever asks again, just calmly say no and keep away from specifics as this will probably ignite an argument which wont do either of you any good.