Need advice stopping breastfeeding

Hey y’all, so my son is 18 months old. And he’s co slept with me since he was a nb. Dad rocks him to sleep in the chair and then brings him to me and he’ll wake up for a second and start sucking my boob eventually he unlatches and turns over or just falls asleep. It’s like this at bedtime and nap time. Someone rocks him and brings him to me in bed. The only times through out the day he drinks from my boobs is nap time, bed time, and when he wakes up in the morning. How do I get him off my boob? I don’t think it’s the milk he’s interested in it’s just the sucking motion. I’ve tried just putting him to sleep without my boob sometimes it works most times it doesn’t. Any advice would be greatly appreciated.