Formula debate

So I've been trying to breast feed as much as possible but everytime I pump I get really bad cramps and get nauseous. So I haven't been so successful but, I'm still trying to do my best. She probably gets 3 bottles of it a day.

In the meantime she has been having similac since thats what the hospital uses. The hospital loaded us up with it before leaving and after the 3rd day we will be running out. All I have now at home is Enfamil. Now I'm questioning if changing to Enfamil will be ok or keep her on Similac since thats what shes use to. Otherwise idk if switch is any different. Any suggestions, ideas, or experiences? Thanks!