Dilemma (leave your honest advice)

The other day I caught up with the last boy I was in love with (from 3 years ago) because things ended badly and I needed closure, nothing happened we just spoke. I don’t plan on getting in contact with him ever again either. However... my boyfriend doesn’t know I went and seen him and I have felt so guilty the past 2 days over it. I feel as if I should tell my boyfriend what I did but I don’t want to hurt him and make him feel like he cant trust me. I needed to do what I did, I have many reasons, but even if I explained the reasons to my boyfriend he’d still see it as if I broke his trust and it’d hurt him. Should I tell him or not?