Lactose intolerance???! PLEASE help

My baby is three weeks old. She was on gerber good start gentle but her doctor switched her to soothe due to constipation issues. She has been on this formula for a week now and is still not pooping daily, when she does poop it’s super dark green, extremely fussy 24/7, cries while eating, and you can literally hear her tummy gurgling all the time. :( She also is always trying to eat, like the formula isn’t filling her up! She’s eating 3-4 ounces every 2-3 hours and still trying to eat more after finishing! Do you guys think I should switch her to soy formula? Does this sound like lactose intolerance/sensitivity to you?