advise:( none stop baby thoughts

I'm only 18, been with fiancé 2,1/2 years and I want a baby so badly it hurts. Sometimes I hold my belly and convince my self I'm pregnant then I realise  I'm not. It's constantly at the back of my mind all I think about is a baby, baby names baby clothes it just won't go away. I wake up in the night because I've thinking about baby names in my sleep and I sub consciously think about names and remember to tell my partner in the morning? Why is this. Financially we arnt exactly ready.:. We would manange but not be comfortable. And emotionally we feel ready?