In answer to your initial question, it really doesn't sound like you are doing anything wrong

We never know what is going on in other people's lives, even our close friends still might hide things from us. In a group like that, it can be hard to break down the existing barriers.

I joined a playgroup recently and it was an existing mothers' group that had morphed into a playgroup. Fortunately they were extremely welcoming and friendly. But not all are - I hear stories like yours quite frequently. I think for a lot of us, if we have a group of friends that we see once a week, it can be easy to just stay in our comfort zone and chat with them. Maybe, like you, they struggle to build a new friendship? Aren't feeling up to building new friendships?

I think you need to get back on the morning tea and activity roster. Our PG does the same thing, one mum does the activity and another the morning tea each week, and it has been a great way to get all the mums sitting with their kids and then chatting while the kids do the craft.

I sympathise with following your DS around - my DS2 is the same, he needs constant supervision, so I often feel like I start a conversation with someone only to have to run off and chase DS2 before he disappears/falls off the slide/tips over the crazy coupe/whacks another child.

I know that the other mums don't have that problem as their kids are older (mostly) and can be left to play independently and often end up sitting around and chatting. Could it be that is also affecting things? What ages are their kids?

At the end of the day, as others have said, check out some other options. I totally understand wanting to do the local thing - I was travelling 30mins to a PG for a while and then went "This is really silly, there must be something closer to home" - but if it isn't working out for you, is it really worth taking DS?

What about your local ABA group, do they run meetings? I have found most ABA groups to be very welcoming and open - regardless of your feeding status, by the way. Everyone is welcome, normally.