I need advice

I am in disbelief right now. I actually don't know what to do. My fiancé hhas been dipping every Wednesday for.the past.couple months and I found out about it not too long ago. So last night he promised me it would just be an every so.often thing like when he's drinking with his friends. He also said that he rarely smokes weed. Tonight we were supposed to do something together after the loss of my kitten. He was supposed to.come home after golf. This is something I knew I couldn't do by myself and he said he'd be there. No. Instead he went to his cousins apartment and got drunk and high and I told him I was coming to get him. I found him laying on the ground outside of the apartment. His cousin just left him there. I couldn't pick him up myself so I was banging on his uncles apartment door trying to get help. When I went looking for his cousins number in his phone I found out that him and his friends plan on taking aderol on their camping trip. I finally got him home and found a brand new thing of dip in his pocket. I feel like I don't know the person I've been with for over 6 years. What would you guys do in my situation?