My son is lactose intolerant so he was put on soy formula. I can't breast feed so that's out of the question. Being on soy has caused him to be constipated for the last week that he's been on it. He wakes up screaming in the middle of the night 3 or 4 times trying to poop and it comes out in solid nuggets. Will this go away after a while or is there a different formula I can try?