My DS always nurses to sleep, and when he got a cold with terrible congestion a while back it really threw him off. He just about quit nursing for 3 or 4 days, and it took a week or so before things were back to normal. I'd say especially considering you are moving, just give him time to get back in the groove, or find a new one. Transitions are so hard for toddlers, they really like their familiar surroundings. Maybe you can offer soothing alternatives, like reading books or cuddling with stuffed animal while you sing lullabys?