Anyone else's SO have kids, and how do you feel about them?

My boyfriend and his ex adopted a baby when he was born, he's now three almost four. He gets him every Wednesday and every other weekend. We've been together almost a year now. And I love his son like my own. I suppose he likes me too, I mean he's three lol.

When he has his son, I usually let them have their time together. Though we sometimes do things as a "family". But lately, I've been getting jealous. I know it's selfish of me and he always invites me to spend time with them too. But he barely gets to see him and I don't want to intrude on their time. I told him that I am jealous of his son, and he thinks it's silly and nobody should be jealous of a three year old. But I am.

I suppose if we were married and had our own place, I wouldn't feel the way I do about his son. But I'm just his girlfriend. I always feel like I have to compete for a place in my boyfriend's heart. He's already told me that his son will always come before me. And I totally understand that and have accepted that fact. But I'm still jealous lol.

Also, maybe I'm jealous because he's got his son and I've got no one. I have baby fever and he knows that. I've always wanted to be a mom ever since I was little. He says one day one day... and honestly I'm getting impatient 😩😭