My youngest is 5 so it's been a while, but I nursed both of mine until 21mos each. I remember that I would slowly cut back the nursing session (whether it was nap or bedtime). I too nursed in a rocking chair in their room. What I did was sing a favorite song (like twinkle twinkle) and told her I'd singing it x number of times and when I was done it was time for nap. Every few days I'd reduce the number of times I was singing that song, shortening the nursing session. Eventually I went from signing once to not singing it while sitting rocking chair but singing it while putting her down in the crib. A song like twinkle twinkle is so short that the cut from 1 to none wasn't a big leap. I think I shortened the # of repeats every 3 or 4 days.
I would guess that he associates sitting in the rocking chair with you with nursing. So if you are going to read and rock in that same chair but not nurse he's going to have a hard time with that especially if that's the routine for bedtime. Maybe change up the nap time routine and make it a bit different from the bedtime routine if you are still going to nurse to bed?
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.