Baby fever but not TTC!

Me and my SO are not TTC cause we are not ready we are still young im 18 and he is 23. But for a long time i have had alot of baby fever. I think about what i would buy, the names and just everything that is to do with being pregnant and having a baby. I took a pregnancy test a week or two ago and it was negative. I got upset and i think my SO noticed and he said we will have kids in the future. Everytime i see young girls on my facebook post pics of scans, baby cloths etc i get a little jealous :P have any of you guys been like this?  i feel like im going crazy :P