For the last 3 days Spencer has screamed the entire day, weather he's being held or not. My DD had colic, but hers was only in the evenings, not all day, and I can't remember at what age it started. Could he have colic? He arches his back and pulls his legs up. He passes a lot of gas too. Or could it be the formula? If I switch brands, do I mix them together, or just switch cold turkey? Anyone have any suggestions for which brands are better? Right now we are using the costco kirkland brand. When we introduced formula to DD ( she was much older, 8 months) we used the goodstart with the probiotics, but that stuff is so expensive I was hoping to get away with something a little cheaper.