Wtf is this?

This happened with my first child and now my second. After giving birth, when I see my friends and acquaintances have their babies, it makes me want to cry and I don't understand it. I'm happy for them but overwhelmingly sad at the same time.

I feel like I probably had undiagnosed ppd last time, my emotions were a lot more out of control etc. But this time around, I feel pretty much fine and normal except for this one little thing.

But this one little thing really bothers me. Why would I feel anything other than happiness for them? I don't even remotely understand it. I have to avoid their facebook pages bc even though I love baby pictures, I don't like the feeling I get at all (and looking at strangers pictures doesn't get the same emotional reaction) it's also a diffetent feeling than the teary eyes I get watching a movie scene of baby being born etc. That feels very normal but for some reason this feeling does not.

Someone please tell me I'm not alone and it's okay to have these weirdly mixed feelings about friends giving birth less than 2 months after me..?