Hi SL, I am very much afraid you are not alone in believing your x, hook,line..... It is hard especially when you didn't use your own lawyer but what is done is done unless you feel you really were cheated then maybe a visit to a lawyer might be a good idea. You now have to concentrate on you and your son and rebuild a life for yourself. This is not easy but there is no alternative.
Not sure why you think H should be buying summer clothes for your son when he is 18 years old. Has your son got special needs or physical problems? He is old enough to be working perhaps at least part time if he is still at school. I really would do as others have suggested and not let him talk to you about his father,at least tell him you would rather not hear. Some children sad to say play both parents off against each other. All this will not be resolved overnight so take your time but at least have some goals to aim for.