Hey, its completely normal for you to feel this way. I don’t whether I have the best idea for you but I want to help you. So firstly analyse him on the degree of his honesty and his commitment of being honest. That even if he feels to do something which might be not acceptable to you, he should come forward and say it. Check upon the way he his honest about himself. And why he really chose that path in his past. Was there something serious or he just did this for fun?
Ask him questions, frequent random questions about situations that how he would react to it.