Am I wrong for ending my relationship with my fiancé because he.....?

My fiancé and father of my only child has put me in a tuff spot.

We’ve been together for 3 1/2 years and ever since I met him I’ve expressed to him my hate for drugs(coke) specifically. All these years he has been agreeing with me about how disgusting that drug is and he promised he has never done it or will ever do it.

Well for Christmas we had a party in my house and him and my boy cousin lock themselves in the room. (Everybody In my family knows my cousin does coke) I was soooooo embarrassed ! Why would you lock yourself in our room when I told

You I don’t want him doing that in my house.

Well long story short my mom and I made my cousin confess the day after the party if my fiancé sniffed

With him and he did 😞.

I am heartbroken and don’t know if I am going too hard on him or if I am doing right. I love him deeply but I feel betrayed And disrespected.

What would you do??