Am I the only one getting post-jealous?

I'm in a relationship with a great guy, I seriously think he's the one. We've been in love for a year and he's the first man I've had sex with (I'm bisexual so I wasn't a virgin when I met him), this is my first serious, adult relationship.

My boyfriend is seven years older and he's been in two long relationships before me. The thing is, I'M SO JEALOUS of those girls! Every day I think about how they planned their future kids names just like we do, had sex on the same mattress as we sleep on, etc etc. Anyone here who has the same issue? I know it makes no sense, there's a reason why he isn't with those other girls anymore, and he truly loves me for some weird reason - but I can't get his past girlfriends out of my head. Please tell me I'm not the only one! 😂😭 Or talk some sense into me or whatever because I'm tiiireeed of these thoughts 😩