Ughhh

My fiancé got home from work today and kissed me and I smelt weed on his breath. I have no issues with weed in general but he cant be smoking because his job randomly drug tests. He told me before he never smokes. I asked if he smoked weed today and he said no. I said dude I can smell it. He said no again then finally admitted he took one hit in his buddys car after work. I cant believe he just sat there and lied to me at first with a straight face. And I think he took more than one hit because he was eating like crazy. And I know his best friends at work are huge stoners. He told me that he lied because he wanted to save an argument. I'm kind of pissed here.