Lost friends since being a mum

You aren't overreacting. I'm 36, had my LO almost 9 months ago. My oldest and best friend, known each other since I was 18, never once checked in on me (visit/call/text) when I was pregnant. O she congratulated me on FB when I announced I was pregnant and when I had given birth. But she's never seen her. Never asked how I am. So snip snip, off she can f**k. I am going to meet up with her and find out what the issue is, I need closure.
Message them, and ask them to come over, either together or individually so you can talk and tell them how you feel and find out why.

I’m still in touch with my friends who have kids, but I've drifted apart from those who don't. I guess it’s because our lifestyles are so different now, but it still makes me sad. I think that’s why people try to make new 'mom friends' who can really relate.

This is hard. It's such a shame to drift apart. Have you messaged them to ask how they are and what they're up to? Could you invite them round for a cuppa/ picnic in a park/ coffee/ walk etc. It is difficult when your life has changed so much, and until you go through motherhood yourself I don't think others can truly relate or know how isolating it can be.