My almost four year old still would wake up to nurse. She just self weaned about a month ago. I would try to make it as gentle as possible. Try cutting out the non-important feelings, like during the day. Leave the most comforting ones for last. That may include the bedtime feedings or the middle of the night ones. Once you go all day with out nursing, the others can soon follow. You may have to come up with another bedtime or nap time routine though, especially if he's used to nursing around those times.
I would let him fuss it out a bit, but I know not everyone is comfortable with that approach. If that's not for you, then maybe start with the daytime feedings as others have suggested-stretching out the time between feedings until he's weened. I'm sure you are exhausted. I wish I could think of something that would be a more immediate solution.
He's 15mo and refuses to go back to sleep If not fed
The night feedings are the worst. He's up twice still. do I stop those last?
My son self weaned at 17 months. I just stopped offering it to him until he asked for it, it cut out a lot of feedings because he would only nurse for comfort. If he asked for it but wasn't really upset I would offer water in his favorite cup and he would be glad to take that instead as long as I held him. Hope this helps :)
With my son I was ready to wean at 20 months, he still wanted to keep on but I just couldn't do it anymore. I cut out night nursing at first. It totally sucked for a week or so but he got used to it. I allowed him to nurse first thing in the morning but said no to any other nursing session and offered him something to drink instead. After a few weeks he just stopped asking all together and didn't care to nurse anymore. It was easier than I thought it would be, you just have to be consistent and don't give in.