Hi M.,
When I weaned my older son off of night nursing (your son is NOT too old for nursing, but also doesn't really need to be fed at night), I did a few things. Here is what worked for me:
I made sure that he was nursing & eating enough in the day. We finished the evening with cereal & then I nursed him to sleep.
During the night when he fussed, I learned to listen to see if he was just sort of fussing "in his sleep" & would eventually go back or if he was really waking up. I was always so quick to get up & go to him prior to night weaning - sometimes too quick because he wasn't always necessarily waking up - just making some noise.
I'm not a "cry it out" person so I knew that wasn't going to work for me. I turned to "The No Cry Sleep Solution" for advice.
When I started listening to my son before going to him, sometimes he'd go back to sleep & sometimes not. When he didn't go back to sleep (I never let him get to a full-on cry), I picked him up & cuddled/rocked him back to sleep, but no nursing.
Eventually he woke up less at night usually not at all. My goal wasn't necessarily all night, but I really didn't want to get up more than once with him. I know it isn't that easy for everyone, but that worked for me. I do know that, if you wait until the toddler years to wean night feedings, it is MUCH much harder.
By the way, pediatricians often consider "sleeping through the night" to be six straight hours - I know it doesn't seem like sleeping through the night, but I guess it is! I also had to be mindful of when I was going to sleep after my son went down. Sometimes I was my own best enemy by taking advantage of the "alone time" & not going to sleep myself.
Good luck! I hope you are sleeping longer soon.