Night time separation anxiety

My friend, Pam and I were agreeing on how nice and easy it would be if babies are born with a sleeping reflex and not a learned skill they have to go through. Elliott has been a good sleeper for the most part. He slept through the night by two months and has been sleeping 10-12 hours since three months. He still sleeps the hours but I am guessing it's separation anxiety because he cries numerous times the first couple hours of sleep. When I get there, he usually would fall right back asleep. The last couple days he wakes up and would sit in his crib. He must be practicing his new skill! I became THE person who can feed him his night bottle. He won't let anyone else. I am happy because I know we have a strong bond!! Sometimes I do wish to take a break and let Daddy feed him. Yes, all this whining... :)