Why do I want a baby? I'm only 15.?

I'm about to be 16 and I want a baby soooo bad, but I know this wouldn't be the best time & the best place. I'm a sopre, no job, no house, and no money. I've had quite a few pregnancy scares and every time I took a test I hoped it was negative but I always told myself if it was positive I'd take responsibility. But every time it said negative, I fell on the floor crying. Idk why. But I mean, I love babies, I go to walmart or just anywhere and look at baby clothes & strollers etc., I already bought pacifiers and socks for my baby I mean I'M OBSESSED. My bf wants a baby now too but he agress it's not the best time but he said if I ended up preggo he'd be there for me more than he needs to be and I thank god for him cuz that's rare in a 17 yr old boy. But can someone explainn to me why I want a baby so bad at my age?