Try playgroups with little one and start building a new network of mummy friends - honestly it’s so helpful to have other mummies in your area and it makes it all a lot less lonely. Sometimes we do lose touch with friends as we develop through life or circumstances and different stages in life mean there’s sometimes a pause in friendships which pick up again later. If you want to continue to connect with them still, send messages and arrange things you can do with baby (lunch, coffee, early dinner, early pub visit) or arrange night out without baby.
This is something I've been worrying about with my own friend group - most of them are childfree which I never thought twice about, but already I can feel this sort of distance/exclusion from them for socializing etc. I'm so sorry this happened to you, it's a big reason why I got this app. I want to build my friend group with people in a similar place in life so if my current friends start slipping away, I won't feel completely alone.
I think this is pretty common. A lot of my long term friends all disappeared slowly when I had my first son 4 years ago. With my second they were all gone completely. I didn't even received a congratulations from them when my 2nd was born 🤷♀️, most of them have never met my oldest. If you really care about them maybe is worth asking what is going one. I did ask my best friend the reason why she wasnt getting in touch as much and she said she was scared she would be bothering me knowing how tired I've been. I care about her so if I spend a long time without hearing from her I always call/text. The rest of them I couldn't care less. But I can tell you, you will make new friends. Just be patient and keep look 🙂