Wanted to get this off my chest

24f, I've been carrying some guilt from something that happened when I was younger,ie around 10 or 11years old, I was kissed by my cousin a few times, and it's something that has always weighed on me, I know now that it was inappropriate. and I deeply regret it.

And now I am in a relationship and am not sure if I should share this with my boyfriend, concerned about how he would react. Or Is it better not to share with him?

It really makes me feel like that am i being unfaithful or not honest to him. So need your opinion on this.