mental and physical harracement by husband

I was married from past 13years, I was working and had bright career. But after my marriage come to know that my husband is drinking and smoking too. I opposed but he told that let's have baby I will quite everything. Till date it's same situation no change now things are getting worse he drinks and then he started beating me and abused me. Also everything happened in front of my 12years old kid. He also do same with him. Please suggest me what to do. How
I can change the things. My son wanted to stay with us. I wanted make him cry for us and value of family in life. Please suggest the better way out.