Hi A.,
First of all, remind yourself you did the right thing and that everything will settle in...soon. Remember, even at his young age, your son is very loved and capable of making adjustments, just like you are; not only with a pacifier change but with adding a sister to his life. You are very blessed to be right here, in this double transition. And, in transistion, it normal to have self doubt and fear---but fear is just a breath away from EXCITEMENT and self doubt a thought away from "You can do this!", "You are capable!", "You are ready!" "This is going to be a wonderful change!". The latter thoughts he can pick up on and they can help him through this transition.
P. Jackson, Life Coach