Sleep issues

Little Cubby slept from 8pm to 3:40am last night then woke up again at 8am. I am very excited since he has not slept the whole night since he was born. I usually have to get up three times a night. The doctor isn't any help he told us we are in the separation anxiety stage and we have to go to him when he cries. I am exhausted. I am nursing still but I am not making enough milk so I have to try to supplement. Little Cubby likes to nurse for comfort. It gets very tiring. He will use the pacifier sometimes but nothing compares to mommy. Any advice on how to get a 9 month old to drink formula?