Mum's of more than one?

Ok so i am starting to worry that i can't love my second born child as much az i love my son.. My son is 2 and he is my entire world, i literally love him more than words can describe and i am starting to freak out that when my baby girl is born i won't feel the same way about her... I just can't imagine loving anyone as much as i love my son.. I will obviously love my baby but I'm just not sure it will be the same.. Has anyone else felt like this? What happened when you're second child was born?