formula

What do you guys think of this formula?? I'm a first time mom and my baby girl is 2 weeks old and on similac, but she seems constipated. Every night cries non stop and I can See her face struggling like she's trying to push and making faces. I feel so bad because it looks like she is in pain. So I think I have to switch formulas and idk what else is a good brand but I was using google to do some research and I came across this brand. So any input on it or on a better one that you know of???