a simple solution if he is being stubborn and refusing to climb the stairs would be to walk on without him. he will probably cry and wail but if he realises you are serious about walking off without him his fear of being left alone will probably outweigh the desire not to walk, and he will follow you. it will probably take a few tries to convince him that you wont carry him anymore but it would be worth it if you are planning another baby as you will certainly have your hands full then!