Hi E.,
I'll tell you what I did with my daughter and then hopefully it will give you some suggestions on things to try with your son.
First, congratulations on still nursing! That's wonderful! You're giving your little guy such a great start to life.
I'm guessing since he is more then a year old you are also giving him solid foods. Now that he is over a year, solids are becoming more important as far as his caloric intake. The whole 'nursing enough during the day' thing, as far as all I've read, really has to do with babies younger than 12 months. Before that 12 month mark milk should be their primary source of nutrition and calories.
But, you're beyond that. So, really ... anything he takes is bonus! My daughter continued to wake in the night as well and wanted to nurse at this age. But, of course, after more then a year of not getting a solid 7 or 8 hours of sleep, I was more then ready to give up those night sessions. I was completely prepared to nurse during the day until 2 years....if my daughter wanted to. I was concerned that she might be hungry in the night... I knew I had to determine whether or not it was night waking because she was used to it, or if it was because she was hungry.
So, I started making sure I was alert and awake when she woke up and I started really paying attention to how she nursed. Was it different then during the day... how long, how vigorous, etc... I realized... she was not really taking any milk. It was comfort nursing.
So, I felt good about the amount of food she was getting during the day... no need to adjust that, and I knew I just needed to do something about this comfort nursing.
Some people may tell you to just leave him in his bed and let him cry and eventually he will get it that there is no night nursing. That's not my approach. I felt I needed to continue to let my daughter know I would be there for her, but also teach her that night time is for sleeping.
So, once I determined it was comfort nursing...the next night when she woke up as usual I went in, I made sure her diaper was dry, I sat in the rocker with her, she signed for milk and I calmly told her 'It is not time for milk'. Then I encouraged her to snuggle in and I rocked her.
Yes, she cried. But not too much. I just kept telling her 'it's sleepy time, it's not time for milk'. We did this for about 3 nights. Once she would settle down and be very sleepy again, I would put her in her bed. After about 3 nights... we were good to go.
No more night wakings. She's now 21 months old and still sleeps like a champ. She also doesn't nurse at all anymore. Around 17 months old she started to just drop more and more day feedings until she just didn't ask for it any more. On her 18 month 'birthday' she literally didn't ask for anything. The next night she did (she was down to just bedtime nursing), but was off and on for about a week...and then was totally done.
Hopefully I've given you some things to try. Good luck!