Relationship and drugs

I recently found out my husband has been addicted to heroin the whole length of our relationship. We are married with 2 kids. He checked into rehab on Tuesday and says he wants to get better and to change. What would you do in my situation? This has seriously been the hardest thing I have ever been thru. I am mentally, physically and emotionally drained. His family has said if he relapses they will disown him. This is his one and only chance.