How can I ask for help

I'm currently 25 weeks and am over and done with being with my husband. I can't stand being with a drinker, smoker, cocaine user much less now that my baby is on the way. I'm tired of it and I want to move back with my parents. They're mexican and are extremely strict about marriage and don't believe in divorce. I got pregnant out if marriage and they didn't react as bad as I thought they were really supportive but I'm scared they will be really upset if I get a divorce I'm sure they'll understand why once I explain the reasons why but it's jsut scary to take his type of step specially with a baby on the way:(