I think a lot of the loneliness has to do with location. I'm in the Bible Belt and got married young. 5 out of my 6 bridesmaids have kids already. I showed up for all the baby showers, the first birthday parties.....but eventually the invites stopped coming. I don't think it's malicious - I just don't fit anymore. My partner & I thought we wanted kids, but I'm not well enough. So the community I planned for is just....not a thing, and I'm still grieving that.