Teen mind stuck on having kids

I'm transmasc, but nonbinary. I'm also pre-everything for now. Anyway, it seems like sometimes my mindgets stuck on having kids, like actually giving birth to them,names,what they would look like depending on which of my DFs is the other parent. I feel so bad and it makes me feel less masculine. I'm only 16,why does this happen? I really shouldn't be having these thoughts, I'm not even out of high school