Is this normal?

Darlene • 24, Single Mommy to a beautiful baby girl born on June 14, 2016💓
EDIT: I forgot to mentions she spit up after every single feeding and sometimes throws most of it up. 
My daughter is going to be 2 months and ever since she was born she's been a grunter when she eats, towards the end of her bottle she's really fussy and moves around a lot but she still wants to finish. And she's only eating about 3 ounces, sometimes 4 before bed, I feel like she should be drinking more than that by now.  She doesn't have diarhea but she always sounds like she's struggling to poop or fart and this is after every feeding. And when she does poop she does not look constipated. I don't know if it is normal? Or if it is her formula...she uses regular enfamil. But I'm thinking of switching her to similac sensitive. Are there any moms who like it? And do you recommend any other formula? TIA!