I think people on this thread are being horrible to you OP.
I have 2 young children and I am not too busy to send a message to a first timer mother asking how she’s finding it, and chatting through anything she wants. I was in the middle of the having children thing with my friendship group, and those who had had children even several years ago made a big effort - offering me a baby bouncer, advice on breastfeeding, telling me if stuff was normal or not etc.
Those friends of mine who have had children after me I’ve been in regular touch, especially during lockdown when the other support they might have will be less available. And I am actually genuinely interested to know how they’re getting on.
If you were after daily messages then yeah that’s a bit much, but wanting someone to ask after how you are finding motherhood and how your baby is at some point between them being born and being 6 months old? Yeah, your friends are self obsessed dicks. Especially given you had to overcome your personal upset at the time of not having your own kids.
See also: people who get married first and want a bit fanfare but by the time their friends (who came on the hen and made a big effort to be good guests at the wedding) get married, weddings are old news and they can’t be arsed to repay the favour.
Being at a different stage of life is no excuse. When your mate has something going on, you make a reasonable effort to be supportive and interested. Your life doesn’t have to revolve around it, but don’t be totally absent FFS.
I’m sorry OP and congratulations on your baby 
Also as an aside, my sister is in her mid 20s, her boyfriend his late 20s and they and all their friends have Facebook so what am I missing there?!