I have asked this question in The Workplace, but it didn't seem to be the good place for this question, so I'm trying my luck here.
I have been working in the place I currently am for more than a year now (IT sector), and since a few month, I have the feeling that I'm being left out. We're about ten in the room where I am, and we're using Slack to communicate. However, it seems that there are lots of conversation groups between the other colleagues, and I'm in none of them, while the others are at least in one of them (excepted the main big ones, such as '#random' or '#general').
Since I'm here, two new guys have joined the team, and it looks like they got better integrated that I was / am: for an example, when the rest of the team decide to go to a restaurant for lunch, they ask everybody one by one... except me.
Maybe I happen to be the weird and lone guy, or maybe it's because I've done several (not that) small mistakes in the past that made everyone lose their mind (me included), but even since before, I have this feeling that I'm missing out a lot of social stuff that seems to be happening right next to me. Maybe it's also the context and the project that have been assigned to them that integrated them more.
The only person I could talk about this is the lead developer, anyone else would be a weird choice (manager included). My question is, how should I approach him?
My goal is not really about making friends, it's more being naturally involved in events.
UPDATE
First of all, I realized that I tried everything you guys suggested beforehand, and I didn't put it in my original question, sorry about that.
I also managed to speak with the lead developer. For the context, I'm way closer to him than to any manager in this society, that's why I mentioned him. He apologized about the lunch at the restaurant, and told me that many factors (not linked to me, but more about the project, how we are arranged in the workspace, the persons that work in the same project, etc) made him kind of forget me, and apologized once again. I feel relieved now, thank you all for your suggestions!