Help! Lactose intolerant or milk allergy

My little girl was diagnosed with acid reflux and is now 11 weeks. At 7 weeks we switched her to Gerber soothe which was amazing and made huge difference with tummy troubles. At feedings she is now squirming and getting red faced and straightening her legs and even stopped feeding through her bottle this morning and started screaming. She has screamed all day and draws her legs up to her abdomen then straightens them back out, she has also started spitting up curdled milk that smells like vomit and she didn't used to spit up curdled milk even with reflux,  it's like something isn't digesting right or taking a long time to digest. She's on correct dose Zantac for weight and doesn't cry when spitting up like reflux. Just randomly starts screaming and drawing legs up to tummy. Any help?? Dr says we might try nutramigen if not better over weekend. She also poops once a day so not constipated.