How would you feel if you caught your SO

I came home unexpectedly because I had a break during the morning at work. Caught my SO smoking weed and he tried to hide it from me. Said he’s been doing it for a few days because it “takes the edge off.” I can’t pinpoint why I feel the way I do but I definitely don’t want to be with someone who smokes anything and I feel hurt and like I can’t trust him because he’s hiding it from me.