I dont trust my boyfriend?

He's lying to me about smoking weed after I caught him already once and said I didn't care if he smoked it or not. Also there are txts on his phone from this skanky married girl who would flirt with him at work. We all work together. The texts aren't flirts but I know years back before she got married he did like her and was trying to pursue her. Then after him and I got together she would flirt with him a lot. Joking about naming her baby after him and moving in his house. He really hasn't acted wrong with her and the txts aren't flirtatious but I still feel like he should tell me that the skank at work has been texting him. What do I do? I'm feeling a terrible wave of anxiety when I think about it all.