Is it bad to switch my baby's formula again?

i had her on enfimil for her first 3 weeks and i was planning on getting wic, but her doctor told me that they only give you similac so i switched her and now i don't have to go through wic and she did a lot better on enfimil. on similac she has been more fussy and has had some constipation problems, so is it bad to switch her back to enfimil?