How long does a wife have to put up with being yelled at all the time.Always blamed for everything.?

I always cop the flak over a son who has a anger problem and drug issues.I receive alot of verbal abuse from him and my husband over this matter.Am I being selfish for wanting out and making a peaceful life for myself and my sanity.??MY son is in his mid twenties and gets into alot of trouble but I have done everything possible to help and cannot go on mentally with it.Thankyou foor all genuine answers or advice.