5 month old sleeping habits

My EBF soon to be 5 month old has been waking up more in the last few weeks. It's almost like clockwork: 11:00, 1:00, 3:00 and then he stays asleep until around 8:00 or 9:00. Have I created a habit because I nurse him at night? I know he can sleep longer so I try and let him cry but he freaks out. I feel like this started when I began giving him rice cereal. Ugh I am so frustrated!