Is not telling the full extent of the truth considered lying or “hiding” information?

Hey gals, so my man decided to go out and hang out with one of his friends (who is a girl) after I went to bed the other night. I trust him (and her for that matter) 100%, but just can’t get over the fact that he didn’t tell me. I caught him and prompted him to tell me, and he still didn’t. Finally, I just told him I knew, and he said “oh yeah, I went and hung out with her” and told me that it slipped his mind and he didn’t think about it afterwards to tell me. I don’t care that he hung out with her, but it is really bothering me that he didn’t tell me. He said that he knew it was a stressful week for me so he didn’t want to tell me and have one more thing to think about, but him not telling me is making me overthink more than if he would’ve just told me in the first place.

Anyways, my question is this, do you think I’m overreacting?