Should I be mad?

Ray

I'm going to keep this short and simple. Been dating my bf for about 2 years. He smokes weed occasionally but I just read his messages between him and a friend and apparently he's about to buy shrooms. I don't want him taking other drugs and not fully ok with him smoking either which he already knows. Should I tell him I read his conversation and ask him not to use that drug or what would you guys do?