Hi, I'd like to help you with your question.
It is very difficult to help someone who uses and is not interested in becoming sober. Your son's response to you suggesting he gets help is very normal, however. When someone uses and is in denial that they have a problem, they will use all their defenses to resist any suggestion or request they get help. They feel they have it all under control, when in fact they do not.
The first step is to talk with other family members about what you would all like to do about your son's use. When you work together, you have a better chance of helping your son. One suggestion is to tell your son that you want him to get help. Be ready to provide options for him such as inpatient treatment programs and therapist resources.
If he still refuses, talk with your family about doing an intervention. An intervention, with the help of an intervention specialist or a therapist, is when those who care about your son, such as family and friends, all meet together with your son and confront him about his use. This is helpful in breaking through the denial that most addicts have that prevents them from seeing they need help. Here is a link to help you understand intervention better:
Also, consider contacting Al non and Narcotics Anonymous to get help for your family. The more support you all have, the better you are able to cope with your son's problem.
Set rules for your son and stick to them. If he is staying at home with you, then tell him he needs to complete chores and find a job. Stop giving him money or go out and buy what he needs instead of just letting him have cash. Letting him have money just keeps him in the abuse cycle.
Learn what you can about drug and alcohol abuse. The more you know, the better you can deal with your son's addiction. Here are some resources to help you get started:
Stay Close: A Mother's Story of Her Son's Addiction by Libby Cataldi
Addict In The Family: Stories of Loss, Hope, and Recovery. by Beverly Conyers
You can find these books on Amazon.com or your local library may have them for you.
I hope this helps you,