4 months!

Your baby should be sleeping at least 5-7 hours at night or longer by now! You can go ahead and feed them rice cereal. Just mix a little rice cereal with their milk to a consistency you think they can handle. Don't get it to soupy. Feed it to them right before they take their feedings. This should help them sleep better if you're still getting up at night. Also, you can start to train them to hold their bottle at this age. Every time you feed them, put their hands on the bottle so they can get used to holding it. Give it a little less support than you normally would so they start to realize they have to hold it if they're going to get any milk. If you're still having sleepless nights, (I don't recommend this, but...) you can put a bottle in their bed and that way when they wake up for their feeding, they can fed themselves and you get to sleep! You may have to wean them from this later. Don't tell your pediatrician your doing this. It's not recommended. It's bad for their teeth, so brush them. Best of luck!