It hurts my heart

I can't stop crying with the thought that once Ariana is born, that I won't be able to spend all my time with Alex.  I keep having these visions of him calling my name and him not understanding that I can't put the baby down to read him a book.  I keep seeing him clawing at my husband so he can get to me and Zach dragging him away.  My heart is broken for my son because he does not understand what having this baby is going to mean and it hurt to know that having his baby will be a painful experience for him.  He'll only be two years old.  I know he won't remember it in the grand scheme of things, but it hurts my heart to think about it.