Boyfriend lying about small things

I (25F) have been with my BF (25M) for 7 years. We met in school and have been together most of the 7 years, but did break up for a few months in 2021. This was because he lied to me about messaging people from his course on a social media app. I didn’t have a problem with him talking to people, but said I would like to know if he’s speaking to new people regularly/becoming friends with them. There was this one girl in particular who literally confessed she fancied him in the message, which he failed to tell me about that was the final straw, so we broke up.

Things happened and we got back together a few months later. I really felt it was a new relationship, he seemed to appreciate me more and be more open with me until now. Our relationship has gone from strength to strength and we’ve been talking about getting engaged.

However, recently, he joined a new gym. Due to past events, I asked him to tell me if he follows anyone from the gym / speaks to them regularly. As you can guess, he did not. I found out because some guy posted a photo where my bf was posing with a few others. When I confronted him about the lying, he acted like I was overreacting. I don’t care about the photo, but I’ve asked him point blank if he follows anyone from the gym and he’s lied straight to my face. My point is if he can lie about such small things so easily, what else could he be lying about.

I know it’s such a small lie, but considering it’s a somewhat similar situation to when we broke up, it’s really triggered me. I’m not sure if I’m overreacting for thinking about breaking up with him when our relationship has been really happy and supportive in recent years.

Any advice would be appreciated.

TL;DR bf lied about stupid small things a couple of times and now I’m not sure I can trust him.