baby fever I guess??

Soo I totally don't want a baby right now I am not ready and in my opinion too young definitely not mature enough I'm 21 and can barely take care of myself. however sometimes I'm scared that in the future I won't be able to get pregnant idk why I have this fear but I always do I guess cause there are some times when I really thought I would've gotten pregnant but I didn't. does anyone else have that fear? like I really don't know why I have this feeling? is it baby fever? Or is it a maternal instinct? I legit have a fear of not being able to get pregnant in the future. Am I the only one??