Should I stay and try to work things out or get a divorce?

My husband came home one day and handed me some money in the money was a used condom wrapper. When I asked what the **** it was he refused to answer and finally told me he had slept with my "friend". We have been trying to work things out but I can not trust him at all anymore. I don't know what to do ! Should I continue to try to work things out or get a divorce?! Please help