S-Anon is a 12 Step support group for people whose lives have been affected by someone's sex addiction. One of my friends has been in S-Anon for about a year and it has helped her rebuild her very damaged self-esteem and also given her a very good reality check about what she was involved with, because she crumbled under his emotional and psychological manipulations to defend himself and to belittle her.
If you google "S-Anon" (for friends and family, not SA, which is Sex Addicts Anonymous), you may find a meeting in your area if you are in a metropolitan location.