6 weeks old and not sleeping much at night?

My son is 6 weeks old and wakes up every 1hr45min - 2hr15min to be fed, but his pediatrician recommended making him wait at least 3 hrs between feedings. He will cry until I feed him and sometimes for awhile after also. I can use the pacifier to soothe him sometimes but once it falls out he cries again. Do you have any tips for helping my baby sleep longer through the night?