I snooped and found something strange

I don’t know why I did it, I just went into my boyfriend’s phone and went to his messages and started searching my name, phrases like “my girlfriend”, “my girl”, just to see how he talked about me. I know it was a moment of bad insecurity and I shouldn’t have done it and I already regret it. I’ve been with my boyfriend for almost a year now and never had any issues about trust but we just had our first big fight a couple days ago and I started wondering.

Well there was a conversation with his brother and they were both talking about “their girls” and what they look like. Well that took place in early 2021. I met my boyfriend just a couple months after, but the thing is, he has always told me our first date was the first date he had been on in two years. And he maintains that he took a big break from seeing women for those two years to focus on himself. He had no reason to lie because I had just gotten out of a different relationship a little more than just a month before I met him.

But the real kicker is that his brother is getting married this year to his ~high school sweetheart~. And my boyfriend is going to be his best man. His brother and his fiancé have children. My boyfriend has always told me he condemned acts of cheating but if he casually lies to me and also hides his brother’s affair without an issue, I don’t know who I’m getting involved with anymore. I really need advice, I’ve been throwing up all night.

Edit: I know the girl my boyfriend’s brother was talking about was not his fiancé because he said a different name when talking about her.