what do i do with a constipated 2 month old???

NIKKILEW

lo was on similac senitive and had mucous and blood in her poop

pedi put her on enfamil soy and now she is constipated

pedi wants to now try nutramigen however i wonder if i should try similac soy first. until we figure it out what can i do to relieve her pain from the constipation?????